Do frame sections exist? why not cut out the rotted sections and weld in repo?

[rustybucket]

It seems to be lots of work to remove the entire cab off the body and replace the frame. What about sections that are created and can be ordered and shipped?

 

[NookShneer]

Trail tailor @reevesci has rear C-Channel.

C-Channel Kit

 

[Elbert]

well....one thought is that if the frame is rusted to $ell in one place, its likely got problems in other places. Get a "new" frame....paint it , rust proof it....etc...etc and then swap over your stuff.