newbie w/question

I hate to say it, but judging from your description, I'm not sure the car's worth saving. If the floors are that bad, chances are all the structural strength is likely gone. I'd bet the doors don't fit anymore due to the body sagging in the middle. If that's the case, you can't just start welding in floors because then the body will retain it's mis-alignment for good. I passed on a pair of '67 GT 390 fastbacks (rolling chassis only) a few years ago for the same reason. If you're replacing everything but the roof and firewall, it ain't worth it.