A friend of mine got a free 283 Chevrolet for a T-bucket project he was working on. It had been outside for years and was locked up solid. We filled the cylinders with diesel fuel and let it sit for an hour or so. Then we rocked around on the breaker bar and pry bar on the flex plate and it broke loose. Put some fresh oil in it and fired it on the test stand. It smoked like crazy for a few minutes then quit and ran nicely. He changed the cam and heads and beat that thing like a rented mule in that t-bucket for several thousand miles before he sold it.

Not saying this is a good idea but I would try and make it run, but I think that kind of challenge is fun.