Rust in New Mexico? You poor guy.

Get some 1x1 square 12 gauge or so tubing and weld in as braces on the cab before you cut anything out.

On visible sheet metal, often it is best to replace only what is bad. Just cut out until you get to good metal, then stop.

Normally, this is because the reproduction stuff does not have the nice crisp bend lines that the factory had, and they look bad. On braces and supports that you can't see, it is probably better to replace the entire piece since it is structural, not cosmetic, and if you don't replace the whole thing, you are depending on your weld. A weld is always weaker than base metal and when you weld you have to grind off the EPD or what is covering the piece to keep it from rusting, so you are starting over with rust protection and painting something in the field versus the single piece being covered in a factory.


R-Bo

1959 Apache 1/2 ton Big Window, Short bed Fleetside (under reconstruction)
1966 GMC 305V6 in the family