Challenger Pilot Your frame is made of a-36 frame steel, made to flex riveted to be tuff. Unless it is loosened -up,or damaged (usually from chain hook-ups) I would leave it alone and if repair is needed would rivet like mike says. My 51 3600 has flexed hundreds of times from massive loads is still just fine. GM rivet jobs were done to be tuff and durable,if you repair get a-36 frame steel,also welds good with 7018 low hydrogen welding rod.
