[tmadden2]

My two cents, which are worth probably half that: You don't have a car right now. You've got a chassis and a pile of parts. If you get hit by a bus tomorrow, it's a thing of unknown value with a lot of work ahead of it to ever be a car again. To be a car, the engine needs to be done. The body work sounds like it doesn't.

If the chassis has no real structural deficiencies, I'd skip the rust for now and rebuild the engine to install it as-is. I'd get it back to a state where if I ever wanted to or had to, I could sell it in a week on Bring A Trailer. I'd drive the car for months or years. Whatever rust it has by now will only be marginally worse in a year or two. It won't eat itself in that time. I'd make sure that I still loved it enough to put even more money into it. Once you've got a running car, then you can decide when and how you want to do a paint / body restoration.