Ford introduced the Mustang in 1964 to rave reviews. Not wanting the Mustang’s popularity to be a flash in the pan, Ford decided to the way to ensure longevity was to change the Mustang’s image from a “secretary’s car” to a bona fide performance car. To do that they turned to Carroll Shelby, who was experiencing unparalleled racing success with the Ford 289 in his Cobra.
How did Ford intend to prove to its buyers that the Mustang was a legitimate sports car? By winning races of course. But before that could happen, The Sports Car Club of America (SCCA) had a few requirements for Ford to meet. There had to be at least 100 street and competition versions produced; they had to be two-seaters; and the competition version could have a modified suspension or engine from the street version, but not both. As building a street car with a pumped up race motor didn’t make much sense, Shelby opted to develop the suspension and produce both street and competition versions with the same setup. A street car with competition suspension is much more manageable and desirable versus a street car with a race motor.
And so the Shelby GT-350 Competition Model, or “R Model” was born. Ford couldn’t have dreamed of a better outcome as the R Model dominated B/Production competition, proving to be nearly unbeatable in 1965, winning five out of six regional SCCA championships and the B/Production National Championship.

The R Model is the racing version of the G.T.350 and was only built 36 times in 1965. The price for this master piece was 5995$. Pretty much compared to a regular Mustang which started at about 2500$. Only 1965 Mustang K Code Fastbacks were used and stripped down right at the factory and shipped to Shelby American on Princeton Drive in Venice, CA. The LAX plant was opened several months later.
Here is a list of the differences between the Shelby street version “S” and the Shelby race version “R”

01. No carpet 02. No headliner 03. No sound deadener 04. No heating system. Holes coverd with delete plates 05. No radio 06. Plexiglass rear window 07. Plexiglass side windows operated with a nylon strap in a light weight aluminium frame 08. No C-pillar vents. Hole covered with a aluminium plate. Mounted on the car with 22 rivets 09. No glove box door 10. CS 6 dial instruments: Water temp, oil temp, oil pressure, fuel pressure, tachometer, speedometer 11. Fire proof door panels 12. Fire extinguisher 13. Rollbar 14. A special racing seat could be ordered 14. No bumpers 15. Racing apron 16. Cooled brakes on front and back 17. No windshield wiper water reservoir 18. Steward-Warner 240 electric fuel pump 19. 36 gallon race tank. Two standard tanks welded together with a 3 inch LeMans gas cap 20. Bigger exhaust side pipes 2,5” instead of 2” of the street-version 21. 7x15 magnesium American Racing wheels 22. Goodyear Blue Steak tyres 6.00/9.30x15 23. Galaxy radiator 24. No cooling fan 25. Hayden engine oil cooler 26. Aviaid 6qt steel oil pan 27. The factory and preferred customers got the steel valve covers. The "regular" customers got the finned cast aluminium COBRA covers 28. Shelby modified and tested 289 V8 and track tested