Thank you so much for the information and time John and Paul.
I was under the impression that these lenses would sync at any speed?
Well today I did the transplant. The only visible difference in the shutter assembles I could see was a longer post that mechanically couples the shutter speed ring to the actual shutter.. The longer post was a non issue when re-assembling in a different lens.
Also, the 50mm lens the shutter came from was F4.5, where the 90mm is F3.8. All other speeds line up the way they should. This is just glass performance, right? I measured the openings with a pair of calipers and they matched.
Everything feels good and works well off the camera. Can't wait to test the lens with a few rolls of film in the next couple of days.
Is there a way for a DIY'er to measure actual shutter speed or do you just trust what the selector ring says? Listening to the shutters click at slower speeds kinda sound the way they should.
I'll post some more pictures of the lenses in several pieces when I get home tonight.