this may be way out there, but would it be possible to use a pair of aftermarket [imported] fenders, from say, a mid to late chevy, and cut out the round wheel opening to use to fill in the opening of the big truck fender ?
i know this type fender is basically "flat" in the front to rear plane, but when cut away from the top curvature, and the rear flange area by the door, it may be workable to add to the other fenders ?
i'm no body man, but just throwing something out there as an idea.