...I recently saw the 10 speed Schwinn built up, it was very well done, inspired me to find one, same with the 5 Speed.
As for the Budweiser Rocket, according to Wikipedia, the original car is in storage at the Smithsonian ( the Smith Brothers museum as Barney Fife once referred to it ) a second version with a narrowed track is said to be in the Talladega Speedway museum. So if they wanted to resurrect that effort, it's not like they couldn't find the car to measure.