I was able to reach only one of the retailers by phone, Crowder Customs, and according to their parts guy, the 6002 hub is unavailable, but says as the steering column is 15mm, as is the one in my '78, a 6001 will fit, but has a different height, how much he couldn't say, he doesn't have a 6002 available to compare to. So in order to confirm his statement, I'll have to buy one, and test.
So I'm still trying to find a source for an AMG Momo hub, from back in the day, which we know will fit correctly. If I can't locate one, I'll have to do the above, now known as Plan B. Maybe Renato, or anyone, can tell me if the Nardi/Personal hub will accept a Momo/Sparco steering wheel? That will be Plan C.