Rust repair

[My 86]

I bought a 1986 GMC  1/2  wheel drive last fall. Body is in good shape however it does has some rust on the rear back box panels and of course the rocker panels. There is no rust on the wheel wells like you usually see in this body style. All drain holes are open and you can see the factory coating still there. What would be the best way to repair these areas? Should i use a plasma cutter and cut this out and weld back in or use an adhesive? Looking at using Tabco patch panels. If you weld replacement panels back in is cavity wax good for rustproofing this repaired area? I know there are a lot of professionals and experienced body men on this forum so I appreciate any thoughts and suggestions you may have on this

[1967KaiserM715]

First pic is rear can corner, weld only as is structural.

The last two you can do an adhesive, but honestly if you have to weld the cab, might as well weld here too. Now the reason it rusted there was because of the mudflaps; not to say it won't without them, but the flap location expediated the process. I always tell people who want mud flaps(good idea for salt season) is to make a bracket that attaches to the frame, leaving a little space between flap and fender so nothing gets caught and stays there


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[K20Detroit]

My '84 K20 has rust in the same spots.
I honestly wouldn't agree on the mudflap assumption, due to how my '84 has never had mudflaps (as far as I can tell) yet is 3-4x worse in those areas.
My '79 K20, on the other hand, had mudflaps all its life and was spotless there - inside and out.
The '84 is a southern truck, '79 a northern truck.

[Blazin]

The cab corner rust is not that bad. Can be replaced with adhesive. If they were rotted off, & the inners were in horrible shape weld would be better.
I very seldom use plasma cutter to remove rust. I prefer a cut off wheel.