im a collector and fan of the old 3-speeds wether shimano, sturmey-archer, or sachs torpedo dreigang
im almost sure they are not compatible, ebay is a good source for old shimano 3 speed hubs you might snag one for parts to fix yours, if you have a local bike coop they might have them laying around for small price im not sure if your willing to travel to bike oven/kitchen/bikerowave coops in LA county im almost sure you'll find one there.
i have rebuilt many wheels myself replacing the steel rims with alloys and keeping the original 3 speed hubs and in most case using the same spokes.
the bike coop also can help you rebuild the wheel if you ever go that route of replacing the hub they have Park TS-2 truing jigs and can assist you if you happen to venture into rebuilding your wheel with a different hub
also have a question how did you date the bike being 70s ? as far as I know bike from the 70s use Sturmey Archer hubs and by the late 80s to early 90s they use shimano 3 speed hubs
anyway good luck and hope you get that vintage up and running again.