Like many F150s from this era the dreaded rear wheel well rust appeared. I started this thread to hopefully get some guidance from others and show how I am repairing this common problem. Here is what I started with, does not look too extensive right?

After the wheel well trim was off I found the entire lip was completely rusted out. So I got out my saws-all and cut the inner fender back. Then I used a Black & Decker jig saw with metal blade to cut the panel back to clean metal. After that I cleaned up the opening with a 4.5" angle grinder with grinding disk:

Here is the driver's side patch butt welded in. I used .025" wire with C25 gas, Lincoln Pro Mig 140, 3.5 wire speed, B Volt setting. With the metal shiny clean I did not have too much trouble. I bought the patch panel from LMC Truck and it was nice thick metal. It will need a skim of filler. This was the easier of the two sides since the area was smaller so I did this side first:

Here is the other side with the patch fitted:

So I decided on this side I will do a couple of welds, align the metal, grind some, and then clean up the metal to make it shiny before finish welding:

Passenger's side fully welded in. I will have to work the body lines with filler to fine tune the shape but I prefer the smaller patch, less welding...

Brushed on Rust Reformer cause I need to drive the truck a couple days. The plan it to completely remove Rust Reformer with stripping wheel, work the body filler over the bare metal, and put epoxy prime on both sides of panel and then start prepping for paint. Its looking like all the paint on the lower 1/3 of the bed side outer panels has to come off to insure all that metal is corrosion free. I see three of four tiny dots that look like rust spots, no bubbling, but very suspicious looking. I was really hoping not have to get into the bronze painted areas but since I am keeping this truck I want it to last. Will be removing body moldings too so its easier to block the bed sides straight. Probably take the bed off the truck and put it on saw horses in my detached garage etc etc. Take the truck off the road for a couple months, we will see if I can control this scope creep....

Bed liner out, side moldings off, and I hammer/dolly all the dents the best I could to minimize filler. I have to take truck in for emissions test then bed will come off. Plan is to take all low spots down to metal, apply Evercoat gold filler, block the sides with dura block with 80 grit till they are straight, then epoxy primer, set over night, then 2k urethane high build and block. Many cycles of high build and blocking are planned. Will reapply epoxy every time I burn through to metal....

Bay in detached garage is divided by a temporary plastic wall.

Took stripping wheel to driver's side wheel well back down to metal.