75 Scamp suggestions

First off welcome to FABO. I think your first step is to get it running and driving. Which means fixing the parts that need to be replaced. You would be surprised at what your local parts supplier will have in stock. Bondo doesnt fix rust. Best way to fix rust is to cut it out and put new metal in.

If you have plans in the works to swap it someday I would just give it a GOOD tune up for now and drive it. Keep the money you save on gas and put it towards your V8 someday.