1970 GMC cab floor

[kuhndogg70]

I am in a pickle right now. I have a 1970 GMC 1/2 ton 2wd 8 foot bed pickup with rear leaf springs. I have had it for about a year and a half now and have been working on it regularly. I pulled the interior apart and got the cab off the frame a couple of weeks ago and found a lot of patch work and some not so great repair work on the floor. The rear cab crossmember is pushing in due to rust and will need replaced as well as the rear cab supports and the rocker panels. Is this too much metal work to attempt? I don't have a big welder. Just a gasless mig. Should I try to sell the cab and find one in better condition? Thoughts? Comments?