window regulator repair?

Yes sir, Only when a replacement regulator cannot be found. Drill a hole an inch or more below the center of the bad section. Cut out the bad section in a V down to your drilled hole. Cut a piece from a donor to fit proper and weld it in. The patch piece doesn't need to match and fill the hole. Tip of the patch piece can run wild there. The hole is only to relieve stress and prevent cracking in the furture.
Be warned though, the quarter windows and regulators are the most agravaiting thing you'll ever R&R ( unless its a vert of course ) so find and fix whatever caused it to strip the gear while you're at it.