71 swinger project

Some photos would be helpful so we can see exactly what you need. If your floor is rotted all the way up over the rear axle, you'll probably have to find a donor car to scavenge that piece. There are several places to get replacement trunk floor, spare tire well, and floor pans. Your car is fairly common and there is a lot of new sheet metal available, including quarter panels and wheel houses. There are also a lot of good people on this site with TONS of parts for sale! Good luck with your project, and welcome to the site!