i will try to post a link here to get yu to where you need to go, but the part numbers are 41148169028, or 41148169028, dependin on which side.
i needed to do the same thing to mine, and they just were welded over the existing holes. the jagged edges were removed and then slathered with the compound (forget the proper name of it right now...) and painted over. voila!! good as new and nobody can tell. i also have 312k miles on it, too.
the reinforcements go over top, and are a good idea, but i also upgraded to turner motorsports mounts.
the link (hopefully) is below, but if not, go to real oem and enter the above part #'s.
edit: re-read the op, so the above listed part #'s are for the towers, which will hold the rear mounts. if these are ok, as stated, then adding the reinforcement plates would be sufficient. if there is any damage (as shown in the pic, which i mistook for his vehicle), then the towers would need to be installed. and yes, they can be 'just welded in over top'. mine were.
Last edited by drivinfaster; 01-17-2009 at 08:07 PM.