If at all possible, I would try to get the new 1/4's welded in there. When I replaced mine about a year ago, I cut out the old metal and replaced with new metal and tack riveted it up in there, grinded down the rivets, bondo'd it all up, then did the primer sealer. Its starting to show through somewhat again now. But that could be because its still primer, and or because I didnt clean the inside of the wheel wells very well, and re-spray them with the proper exterior coating.