What would they be worth?

Thats kinda why I'm teetering on the fence line. I don't want to pay top dollar but don't want to lowball him. Its one of those things. If I do get it and it turns out to be a coffee table I don't want a 800+ paper weight

Make the offer. Worst thing he can say is no or give you an idea of what he wants for them. You are not lowballing him, you are taking a huge risk in buying them. Any Muscle car fan knows what a good 340 is worth. Why has he had them so long?