I recommend abandoning your damaged cowl panel. Cut it out, then go to a junkyard and find an intact cowl assembly that you can have cut out and re-welded into your Mustang. This isn't a body piece that is normally dented or rusted (unless the victim of a flying hood, like yours) and you can use one from any 87-93 Mustang; 2.3 or 5.0. Take the wiper assembly while you're there to fix that problem, too. Clean, sand and paint the transplanted cowl then check out
Mustangs Unlimited (
www.mustangsunlimited.com) to purchase a new black plastic cowl cover ($83.) to finish up the job right.
Good luck.