47-55.1 Cowl Repair, How far to disassemble?

[Dongray]

I have some rust holes on the inner and outer cowls that needs fixin but am debating about how far to tear it down. Most of the inner and outer cowls on the passengers side arent bad but when I look down between them there is a hole in the bottom and some surface rust throughout (see pictures). The 4th picture is of the drivers side between the cowls.
My questions is should I just take care of the rust holes on the inner cowl and the bottom of the outer cowl or should I remove a large section of both so the interior can be sandblasted then install new inner and outer cowls? Thoughts?

[mr48chev]

After I took the liberty of flipping the photos upright so I could tell what I am looking at I'd say you are going to want to go into it far enough that you can get rid of all the rusted out areas an at least clean up and use some rust neutralizer on the surface areas to slow down further issues.

Truth is you are most of the way there already.

[dsraven]

if you really want to find out how bad the rust is, sandblast it.
install the doors and do your best to adjust the gaps. then, with doors on and closed, brace the cab so it doesn't warp or twist on you when you do your cutting and repairs. cross brace it if you can, like an X. then take the doors off and that will open up the area so you can work. take measurements with pics so you can get it right when you weld new stuff in. then blast it if that is the plan. start cutting out the bad stuff. don't cheap out and try to save a few minutes by putting a small patch over thin spots, that will come back to bite you later. when welding in new parts both sides of the metal need to be clean otherwise the welding process will draw contaminants into the weld. do small tack welds and allow to cool or the area will warp and it will be harder to fix that if you had taken your time. it is good to have a few things to do on welding day, that way you can spot a few welds, then go do another project for a few minutes until the area is cool enough that you could put your tongue on it without fear of burning, hypothetically.
I had a cab that was really bad. if I were to do it again I may consider a new aftermarket cab. they come with doors as well, already fit. yes they are expensive but start adding up the patch panels, sandblasting, epoxy primer, grinding discs, sanding materials, shop power, wear and tear on compressors and tools etc plus the time it takes to do the repairs. if the cab is really bad do some math or look for another cab. that is unless you really like the big project......