On the rear cab support, you can use a thin sawzall blade to cut between the rocker and the support, and leave the support attached to the floor (assuming it doesn't need to com out because of rust. Rear cab supports are available from the usual vendors, so you could drill out the spot welds and deal with it that way. Just pointing out there's more than one way to skin a cat.
At this point, you may be better off taking the cab off the frame and putting it on a rotisserie. That would give you good access to do your cutting and welding.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
