I wouldn't do that with the fender fasteners. You'd lose half of the adjustment capacity with the larger holes and fender washers. On the inner fender fasteners, the right side is a 2-person thing as the bolts go thru the footboard from inside the cab. Might be a good idea there if you're working alone to tack the bolts to the footboard. Driver's side inner fender bolts are accessible from underneath, so no need for studs there.
