Stu, that double-ended stud is GM #404352, although I've never seen them new or as spares, or tried. The same part is used for location #3 in photo but not shown in mockup. So any of the used Olds engines, and probably most 350/403 Olds in anything, will have 2 of those studs if searching for one, or a few for spares.
I'd send you one free but I'm in Australia. Anyone who has parted an Olds or two would have a few spare.