A few issues in the video above, namely that when I am in the engine compartment noting the steering components.
I refer to the "rack" of the typical modern rack-and-pinion steering setup. The original Mustang ran a worm-gear setup, which goes a long way toward explaining the factory car's waywardness on the road (versus a modern car.)
This recreated and not-original Shelby GT350 racecar build is just about the ideal starting point for most people.
Almost any engine, transmission and interior setup are feasible with such a clean example like this.
1966 Shelby Mustang GT350 Racecar