GM's had to rust more than any other car. The rear fenderwells on all of them went like crazy. I use to work with a guy who had about a 75 Chevy Pickup bought brand new and by 80 the bed was gone. Mopar had problems with the top of the front fender rusting out when the cars were fairly new. Yea all cars in the 70's had rust problem. Beleive or not Gremlins were better than most when it came to rust.