cut it out.....weld in a replacement.
this is a real PITA for our trucks b/c replacement patches arent really avalible, as compared to like a 85 fullsize GMC where you can order dang near a whole new truck thru JC Whitney.
but with a little luck, some cutting and welding, and a little patience......ok ALOT of patience

it can be done.
case in point......my rocker panels was patched w/ paper towels and bondo
after cutting the old crap out and welding in some new rockers
i made the new panels b/c i couldnt find any....they do come up on ebay once in awhile.....but we got a big ass sheetmetal brake and shear at my guard unit so i just made them.
they didnt come out perfect......lets face it...this thing will NEVER win any trophies for being pretty....but ALOT better than it was.