waterproof car cover for a 64 barracuda

No such thing, they all breathe and some moisture gets through. If you use plastic sheeting, it will condense under it. You will be sorry, ask me how I know. Your best bet for outside storage is the climate controlled cocoon kind of deal if you can find one.

Honestly though, you got the wrong body shop. It shouldn’t sit outside period, no excuses. Start the project and finish it with no delays.