G'day Scott, jump onto the "Naked Goldwings" site, there are several single carb threads there, folks are making their own manifolds using PVC pipe and fittings (no sh1t, and it works!) and Volkswagen carbs, or used Webers off eBay and home made manifolds for cheap too. I've seen a small Holley 4 barrel carb in one thread, and it apparently works pretty well too.
I couldn't initially understand how a single carb could be better than 4 separate carbs, but the trick is that with longer intake runners you get a little more torque, which makes for quicker acceleration with a little less top end speed, which is irrelevant on a 'Wang, no-one rides a 'Wang at warp speed, they're a smooth riding bike and meant for long distances, not sprints.
I've got a bare GL1000 frame (I ratted the 1977 rolling chassis I bought for the front end for my 750 and the wheels for my son's CX500 project) and my old "Made in the USA" GL1200 engine and am still thinking of building it into a bike. If I do, I think I'll "single carb" it (I don't have another set of carbs, but I don't like those old Honda CV's anyway) and see if it works as well as the NGW guys are saying. Cheers, Terry.