I did not respond at first as I really never heard of a 'Tremclad spary bomb'.... If you feel the paint is in really good condition, you can block sand, prime, (seal if you like) and paint. I prefer, especially when the substrate is unknown, to strip it to bare metal and start all over. If you feel the vehicle is worth your efforts, do as much as possible to make it perfect- start at the bdginning!! Good Luck! 
