Lethalchem
Actually, they had to do a lot of tuning and fabrication to make the car work properly. It "handled and braked like $%#" I believe was the quote from one interview I watched of the actual mechanics and drivers of the original race cars. The car was not stolen and passed off as their own achievement. They are the ones who made it a household name.
Also, I havn't compared the two versions in the game, but I THINK the should be slight visual differences. The original car was a bit smaller and narrower. Shelby bulked it up a bit and flared the fenders a tad, giving it a more muscular look once he started trying to fit the 427 in it.
The Ace became the Cobra with Shelby's input - the first one was the Cobra 289 with the original 'narrow body'. The 289 was only built by AC, and was badges as such - and all were right-hand drive.
The 289 was succesful in many racing categories as it had low weight, lots of power and good handling. The big block Corvettes in particular, gave Cobras a run for their money, however, and the need for more power resulted in building big block Cobras.
The Cobra 427 was more than just a bigger engine fitted to an existing car - the whole car was in fact redesigned, few parts remaining the same. They replaced the original tubular frame with a twin-pipe design, so the frame featured twice as many pipes as the original. The body was modified with new, much wider fenders and bigger wheel wells, a bigger double grille and many detail differences.
The suspension was consideraly beefed up and the braking system was upgraded to full race specification. A new transmission and clutch housing were used, as well as a new differential unit. In effect, the 427 was very much a different car than the 289, even though they share the basic layout with eachother.
The 289 was only ever built by AC in Britain, but the 427 was also built by Shelby in the US. Ones built by Shelby had the bodywork shipped from the AC factory, though a number of body panels were also manufactured by Shelby.
There were two versions of the 427, and both manufacturers built both - the regular 427, and the 427 S/C ( Sport / Competition ). The regukar model had 425 hp, while the S/C had 485 hp and revved higher. The engines were made from the same basis, but the S/C unit had some more heavy-duyt parts, for example different camshaft.
The only differences between AC and Shelby Cobras were badging and colour options. In technical sense, they were identical. AC has been continuing to refine th Cobra, and builds evolved versions to this day, with later small-block Ford engines. Shelby also made a very limited run of Cobras in the early '90s - they used leftover lightweight alloy body panels they had stored up when manufacturing was halted back in '66.