SHELBY G.T.350SR

The Birth of the G.T.350 Shelby Mustang
Shelby was referring to the race version of the G.T.350 and went on to say, “It’s almost unbelievable, but we can take a G.T.350 around any circuit where we test, and it’s faster than the best Corvettes in full racing trim. You just can’t very well accept that fact, I know, until you drive the car.” Lee Iacocca is credited for asking Shelby the magic question of what it would take to race the Mustang. Shelby replied, “Build 100 of them.” And so the birth of the G.T.350 Shelby Mustang and the Sports Car Club of America (SCCA) BP sports car took place.

Homologation and Legal Approval

History tells us the G.T.350 Shelby Mustang was homologated, which means the factory—or in this case Shelby—built enough street vehicles to meet the accepted production number imposed by the sanctioning body for the vehicle to be termed “legal” and granted approval to race. The SCCA ran America’s National Championship program, and its international rules were governed by the FIA, which said that for the Mustang to compete in the Production Sports Car B Class category (BP), 100 of the cars had to be built and equipped with normal road touring equipment. Because the 2+2 Mustang needed to be a sports car to qualify, it had to be a two-seater, so the standard 2+2 Mustang rear seat was removed and enough cars were built for the January 1, 1965, qualifying deadline.

Production Modifications at Shelby’s Facility

Shelby was busy racing and dealing with his Cobras, plus spearheading the GT40 racing program at the time, but Dearborn wanted this racing Mustang, and because Ford was paying the bills, time was made to get it done. Soon transport trucks were on their way from Ford’s San Jose assembly plant to Shelby’s facility on Princeton Drive in Venice, California. The trucks were loaded with stripped-down Mustang fastbacks, sans rear seats and hoods, undercoating and body insulation. The standard grille emblem was deleted, as were the rocker-panel chrome strips. The cars were painted Wimbledon White, featured black interiors and came with full-size 9-inch rearends, complete with larger-than-standard rear drum brakes. Borg-Warner T10M four-speed transmissions were used, and they came with aluminum cases and tail-shaft housings.

Handling Improvements and Performance Enhancements

These Mustangs were then modified at the Shelby facility under the direction of chassis ace Ken Miles. It soon became apparent that there was more work involved than first imagined. The front suspension was reworked, with the upper control arms remounted for better geometry and to provide built-in understeer, which was designed to keep the tires firmly planted during heavy cornering. The A-arms were dropped 1 inch in position, which changed the roll center and modified the camber, as the lower arms were also moved outboard. These pivot points were relocated to provide superior high-speed handling, albeit with some visible negative camber.

Steering changes included longer pitman and idler arms, swapped out to give a 19:1 steering ratio (3.5 turns lock-to-lock). Additional changes included fitting a mammoth 1-inch-diameter front stabilizer bar and installing Koni adjustable shocks in the front and rear. Kelsey-Hayes 11.3-inch disc brakes with DS-11 pads were added up front.

Rear Suspension Innovations

These Mustangs received lots of attention at the rear with the installation of a Detroit Locker differential and torque-control bars located on the top and forward side of the leaf springs, with the pivot point directly above the spring eye for the best geometry. This necessitated placing these bars inside the passenger compartment where the rear seat used to be. Holes were added to the floorboards, and they were large enough for full suspension movement. These slotted clearance holes were covered with fiberglass panels and trimmed with rubber lips to keep exhaust fumes from entering the cockpit. Special cables were installed that wrapped around the axle housing to limit suspension travel, and the brakes were larger 2.5-inch metallic shoes for more sure-footed braking power.

Engine Performance and Specifications

The engine for the G.T.350 started out as K-Code 271hp 289 with 10.5:1 compression, a solid-lifter camshaft and a dual-point distributor. Shelby added more power with simple bolt-on speed equipment, including an aluminum high-rise intake manifold, a Holley 715-cfm four-barrel carburetor and tri-Y tubular exhaust headers. A free-flowing exhaust system was used with a glass-pack muffler, and early cars had the pipes exit in front of the rear wheels. The carburetor was a center-pivot design, used to help prevent fuel from sloshing on hard cornering. The standard stamped-steel oil sump was upgraded with a six-quart finned cast-aluminum oil pan with internal baffling, adding extra oil capacity and oil cooling for the new 306hp engine. Additional under-hood mods included the addition of an export brace for added chassis rigidity and a Monte Carlo bar to triangulate the under-hood shock absorber towers. A pair of cast-aluminum Cobra rocker covers and a chrome open-element air cleaner also were added. The battery and its mounting bracket were relocated to the trunk, helping to provide the 53/47 weight distribution for the 2,800-lb car.

Tire and Wheel Specifications

The G.T.350 featured 7.75×15 Goodyear Blue Dot semi-competition tires that tested safe for sustained speeds to 130 mph. CS 15-inch aluminum wheels were available at a price of $273 and looked more racy than the 5.5-inch-wide standard steel wheels. A fiberglass hood with a functional scoop was installed, and the grille received a single emblem on the driver’s side. All cars came with blue side stripes and G.T.350 markings on the lower portion of the front fenders. The 10-inch-wide Le Mans racing stripes that ran front-to-rear were optional.

Interior Features and Modifications

Inside, a new three-spoked, aluminum-framed, wood-rimmed steering wheel was added, and because there was no horn provision, a toggle switch located on the dash was used to sound the horn. A supplemental gauge cluster was added to the center of the dash, housing a 6,500-rpm redline tachometer and oil pressure gauge. Seat belts were a businesslike 3-inch-wide design. The rear seat area had a fiberglass parcel shelf overlay, and that’s where the spare tire was located and laid out horizontally.

The Naming of the G.T.350

Legend has it the car was dubbed G.T.350 during a discussion at Shelby American while trying to come up with a name for the Cobra-ized Mustang. Carroll Shelby is said to have asked employee Phil Remington to pace off the space to determine the distance from the office to the workshop building. He told him it was about 350 feet. So the car was officially named then and there—the G.T.350. The name sounded good and soon appeared on every car built. Only designated Ford dealers were able to offer Shelby Mustang G.T.350s, and the price started at $4,547.

The Competition R Models

Competition R models had all the above items, plus an HD Galaxie A/C radiator, an auxiliary oil cooler and a fiberglass front apron, which came complete with flexible ducting that was positioned to feed cool air toward the brakes. R models also featured Plexiglas side windows to replace the standard side grilles, which weighed some 14 lbs each, and a Plexiglas rear window. The front and rear bumpers were removed, as was the car’s headliner, carpet and upholstery. The new rear window was unique, as it was lightweight and also featured an air-gap opening of 2 inches at the top, which allowed air to escape from the interior and was said to reduce drag and turbulence slightly at the rear of the car.

Interior Safety and Modifications for R Models

A single lightweight race-style seat replaced the standard buckets, and aluminum panels replaced the original Ford door panels while the standard roll-up mechanisms and side glass were discarded and replaced with pull-up Plexiglas units. A shoulder harness, rollbar and fire extinguisher were included and were known collectively as the Interior Safety Group. A complete assortment of gauges (tach, fuel pressure, water temp, oil pressure and oil temperature) also was used.

Engine Specifications for R Models

R-spec versions received balanced, blueprinted and hand-built engines that were given more radical camshaft timing, ported heads and big steel oil pans. An air velocity stack with an airtight seal was fitted between the carburetor and the hood, and this engine was rated at 350 hp.

Fuel and Body Modifications for the Racer Version

The racer version also had its stock Mustang fuel tank replaced with a 34-gallon quick-fill unit, along with a 3-1/4-inch tailpipe that would allow for unpressurized fuel feed. The undercarriage was fitted with a drop-down panel that lowered the fuel filler neck directly behind the driver’s side rear tire. Some cars were fitted with special quick-fill gas caps, with a flat-disk design that worked in conjunction with their flat cap arrangement to reduce pit-stop times.

Legacy and Continuation Models

The G.T.350 Shelby Mustang became an instant classic, and its legacy continues with continuation models, which remain popular among collectors and enthusiasts alike. Today, these cars are celebrated for their distinctive design, exhilarating performance, and historical significance in the automotive world.