So, here’s where I’m at with my solution to this problem. For years I have been outbid more than a dozen times for a suitable donor body. I was finally able to acquire a less than perfect shell (gold and blue in photo). I poured the red silicone mold around it and then used that mold to cast the gray and tan resin bucks. After a lot of filling and sanding, the gray one was used to vacuum form the three bodies in the second pic. They are formed from a clear plastic PETG film to the original scale size. The tan one will be cut along the black lines and a 1/4” will be added in both directions to form a body that will fit a modern slot car chassis that is 3 1/4” wide with a 4” wheelbase. I haven’t had time to try it yet with his mold, but I plan on doing a thin slush casting like I did with the Mercoholic pictured last.