The starter housing (376665) on my 58 QD is broke where the starter pulley bolts to it. Is the metal some sort of pot metal? Probably can't be welded. This little motor runs great and looks like a survivor to boot.
Worth a try I suppose.-----The issue with welding something like that is the alignment of that part after the welding is done.------If that fails there are lots of those housings available used.
It can be welded, not easy though. MUCH easier to find a replacement. Place a wanted ad at aomci.org in the classifieds, and a local member should be able to help you out.