340 advice

OK, here is my $0.02. It sounds like you have not yet purchased it. It also sounds like you have not yet heard it run. Unless you are buying a car from a good friend who you really trust, I have a few 'pricing' rules you might be interested in:
1. If I cannot actually start the engine and hear it run, I assume it needs a complete rebuild and reduce my offer accordingly. It is always a bit touchy to tell someone, "It's not that I don't believe you, but...", but you have to protect yourself.
2. If I cannot put it in gear and feel the transmission work and shift, I assume it needs a complete rebuild, and reduce my offer accordingly. Moving the car around also gives you a chance to assess brakes, rear end, etc.
I have walked away from several deals where the seller was basically saying, "Trust me, everything works fine. The only reason it won't start is....." Now, if you want the car really badly, and are willing to take the risk, that's up to you. I just want to warn you that "It was running great 20 years ago, and it only has 50 miles on it" sounds very fishy.