My initial thought was to bolt them into place and then weld them on the outside. The problem is that the weld will be in a crease in the body design. Here's a pic (Sorry I forgot to take a detailed pic). My experience is that it's very difficult to grind a weld where the metal makes a contour line. If I welded it, I would have to grind it down past where it needs to be and then add filler to make the contour lines match.



Here's my thinking. I will bend the flanges in some so that when I bolt on the fenders they will pull up close. I will then spot weld along the seam to help hold it steady, every few inches or so. I don't believe that merely bolting the fenders on will be steady enough to support any type of filler. I will grind the spot welds down past where it needs to be. I will then use some sort of filler to fill in the rest of the gap and shape the contour lines to match the doors. Does this sound like a reasonable tact?

If I take this route, what is the best filler to use? The gap will be tight, but the radius on the top of the fender may make a 1/8" to 3/16" deep fill.