Need 904 assembly help!

Well, the siege continues! I figured out the output shaft and gear train so I wound up with .011 lash, in spec. BUTTTT, (!!) when I went to put the roller bearing on the tail shaft, I couldn't find matching snap rings for securing the bearing. I had one that was the same thickness as the groves, but when I put the snap ring on the inner grove, the bearing would cover up the other snap ring grove, Not allowing any room for the rear one. I found some thinner snap rings at an ACE hardware, and had to sand them down a couple of thou to get them both to seat. That bearing is the one that came off that output shaft by the way. It also has a smaller I'd than the. Bearing out of the 1968 vintage 904 core I have. Ok, so I put the output shaft into the case and assemble the gear train, install the snap ring, then install the tail shaft housing and secure the big snap ring onto the roller bearing. When I went to trial assemble the direct and forward cluthchs and drum, I literally do not have enough room to seat the pump all the way! WTF? I have a 12 inch dial caliper so I started measuring everything, trying to figure out what I have wrong. I could get the drum lugs deeper into the driving shell by trial fitting without the little output shaft thrust washer, but when I put one in place, the drive lugs on the drum are exactly deep enough to be even with the outer edge of the driving shell. That tells me at least I am seating the clutches properly, (or should be?) So I am not sure anything is wrong there. I put the pump into the case without the clutchs to measure what the correct depth would be for the pump when seated. I then pulled it back out, put the output shaft thrust washer in place, put a thrust washer between the clutches, and one on the pump housing per the exploded view in the book. When I put it all together, the pump won't seat, and is .180 too far out of the case! This means I have something screwed up by somewhere between. .140 and .200+++! At this point all I can think of to fix this mess is to buy a core that is fully assembled and was functional, and take it apart, measuring every depth of each component and thickness of everything till I find out what I have wrong. Any thoughts? I am going back out to the shop to sweep up all my hair I pulled out, and hopefully find what is wrong.