Oops, I guess I missed your last post.
Yeah, I just cut out all the rust and riveted to whatever good metal was left. Luckily, there was enough good metal around the perimeter area of the panels that I was able to rivet to the original fenders with any problems.
For the rear wheel wells, I just made new ones. I just "tubbed" the rear fenderwells.
For the front, the inner fenderwells were in good enough shape that I just slit the ends (where they bend down as they get to the outer fender), then bent them so they were flat, and welded the ends to the outer skin that I riveted on.