I'm rebuilding a 80's univega. Tonight I stripped the bike in preparation for powdercoating next week. I bought Nashbar parts (headset, crank and BB) during their Turkey day sale. After receiving them and test fitting, I noticed the BB is rather tight to screw it. I have the ISIS tool but am really afraid of stripping the plastic threads on the retainers. Anybody have any tips on how to get them threaded correctly? Next I pounded out the old headset. The bearing ring that slides down over the steerer tube seems to be just a touch smaller in - inside - diameter then the old one. This is going to make it really difficult to get it onto the shoulder just above the fork crown. Is this normal, would it help if I don't powder coat this area? It's painted now. I hesitate to force fit it. Any help would be greatly appreciated.
Which ISIS bottom bracket? I recall the Nashbar ISIS BB has aluminum cups. Since you've painted the frame make sure all mating surfaces are clean and free of paint that could jam the threads and fork crown.
Try to clean the BB shell threads with a small wire brush. Then use the old BB steep cups to verify the threads are ok.
Note, it's very easy to cross-thread a plastic cup, I hate them. They should spin on by fingers only if the BB shell threads are good.
As for the headset crown race, verify the fork matches the headset. A lot of Japanese bikes back then used JIS not ISO forks.