2 different VIN numbers. Which should I go with?

[JBill]

If you use the frame number, then what will you do in the future if someone wants to confirm that that number is correct? You'd have to remove the body. For that nightmarish reason alone, I'd go with the engine number. If you feel you need the number also somewhere on the body, I'd do as suggested above, and get some sort of plate with the number (the engine number) stamped on it--and run over in the driveway and left in the rain to make it look old and then pinned to some accessible but inconspicuous place on the firewall. Nobody at your DMV would know the difference but Model A people will.