Ya, they look pretty rough. The only areas that aren't rusted are the areas covered by road tar. It looks like the prior owner passed a little too close to a road crew at some point.
Most of the bolt holes had been wobbled out and some had cracked the metal. So, after stripping all the paint, rust and road tar off, I proceeded to weld patches on the trouble spots.
Clamp
Weld
Grind
Cut a new hole
Same process on the other wheel well
I used the POR-15 process to cover everything. I have used it on other projects and if you follow the directions it works great and leaves a ceramic kind of coating. The one problem is that if the item is exposed to UV rays it will develop a white powder kind of coating. That shouldn't be a problem with these wheel wells.
The major problem I had to tackle was an access hole the previous owner had cut into the passenger side wheel well to access a bad blower motor. I guess that was easier than removing the fender. I decided to put a removable patch in there since it was much easier than trying to butt weld a patch in and who knows? I may need in there again someday.
Since this part is completely covered by the fender, I'm not too worried about what the back side looks like. I may put a silicon gasket in there someday, but for now, I have no plans to drive in the rain or even when there's the possibility of rain.
And they ended up looking like this. Now on to the fenders, the doors, the roof the rear quarters, the.....
