Sub frame replacement?
 

I'm looking at a car locally, a 70ish Nova for my son as his first drag car. It's a complete roller certified at 9.90 . It needs a motor, a glide, and an exhaust system and it would be ready to go racing again theoretically. It has a 10 point roll cage and 9 inch ford rear end with Comp Engineering traction bars or leafs. The only thing I can really fault it for is the front floor pans are rusted through and need replacing. If I remember right, GM built these cars as subframe cars. If that be the case what are the odds that the subframe rails are damage from rust? How hard would they be to replace?

Subframe bolts on with only 4 bolts. Not hard to replace. make sure you disconnect the brake lines or you will trash them. Usually won't rust as bad as floor pans. BUT around the rubber mounts probably will need some beef up work.

If it has a cage and is certified to 9.90 I would bet the thing is tied together pretty well and it aint gona be an easy swap....