On the flathead, lots of people seem to think that because it's old it's automatically rare and valuable, but like Uncle Bob said there's a better than even chance that the block may be cracked. When I talked to a guy from H&H Flatheads about a '32 engine (unique, one year production, first V8 Ford) he shared that he never pays more than $200 to $300 for an old stock engine, even a '32, and even then it may be scrap metal. They're worth big bucks when confirmed good and built out with new parts, but until then they're not that valuable. Uncle Bob may chime in here and tell me how far off base I am, but that's my understanding from talking to one source last year.