DAMN! THAT SOUNDS SO DANGEROUS

I feel that if you make the trade it will become a classic example of the reason why you should never break the rule (should be a law), don’t do business with friends or family.

Both of these cars lives are limited and when the first one dies the one with the car that died first is going to heavily regret making the trade, and could feel cheated.

I would point this out to the stepfather as a good reason for not making the deal regardless of the condition of his car. This way you wouldn’t be insulting his scrap yard bound SEL.