I have several wheels that may well fit the bill. The hub spacing I'm not sure about for all of them as many are 70s/80s and so spaced for 5+ speed blocks, but could be re-dished for 4 speed. A few of the possible 4 speed ones are from the right era but are tub fitting, which I'm not sure would be what you're after. I don't think there were that many clincher alloy rims back then (mostly steel) except for the 1st gen Weinmann rim (with uncommon branding) and even those are quite rare. I suppose wheels with these rims would likely have 4 speed specific hubs, but they might also be five speed. I'll see what I have. It might help if you tell us what brands are on the front wheel hub and rim, unless of course it wasn't original to the bike.
I have several wheels that may well fit the bill. The hub spacing I'm not sure about for all of them as many are 70s/80s and so spaced for 5+ speed blocks, but could be re-dished for 4 speed. A few of the possible 4 speed ones are from the right era but are tub fitting, which I'm not sure would be what you're after. I don't think there were that many clincher alloy rims back then (mostly steel) except for the 1st gen Weinmann rim (with uncommon branding) and even those are quite rare. I suppose wheels with these rims would likely have 4 speed specific hubs, but they might also be five speed. I'll see what I have. It might help if you tell us what brands are on the front wheel hub and rim, unless of course it wasn't original to the bike.