Advice on buying a '75 dart.

Maybe I am overly sceptical but I would try to verify if this guy is really the original owners son in law. Thats a good story to tell while demanding a higher price and also distancing himself from the car at the same time. If the title is still in the original owners name he should have some kind of paperwork giving him ownership and the legal right to sign the owners name to transfer ownership. If the title is still in the original owners name and is already signed meaning not currently titled to the guy your buying it from, I say flipper.

This is a good point. I asked him and he said he has a clean title and it is now in his wife's name. The car is not currently registered?