Thank you! I DID have to drive that sucker on there to get it to seat against the oil seal like that. I'll take it off and put a new one on. Luckily, I have a couple new ones. You know, it's much harder when you didn't take apart the old one. I've been building it up on the bench out of new pieces. I usually snap some pics with my cell phone as I take something apart, to double check when putting it back together. With this one, I'm going in cold.

Further inveatigations
I took it apart again. Tried to fit pieces together individually:

* Layshaft fits nice in Bellhousing bearing. Two light taps with a rubber mallot sinks it home all the way.

* I have a pic earlier in this thread where I checked the layshaft in the case and bellhousing for endfloat. Fit like a glove, no problems.

I can eliminate the layshaft.

* The mainshaft spins nice with the main casing and bellhousing about 1/8" apart. As soon as I try to seat the two, it jambs shut. The jambing happens because the Synchro comes down hard against 3rd. I can get it to bind if I drive the Synchro back. Tap it lightly to unstick it...and I'm free again.

* Removed the Synchro and roller bearing collar. Removed the layshaft. Put bellhousing on. It fits great. Slides flush on the gasket surface.

* Add Synchro. Re-assemble. It won't won't go flush, and tightens the Synchro against 3rd.

* Removed the Synchro, and just put the roller bearing on (no synchro) and re-assbled. Again, it won't sit flush.

So, either the mainshaft is too far forward...the pinion is too far back...or the Synchro and/or roller bearing are too fat???

* What are the chances 2 separate parts are wrong(Synchro and roller bearing)??

* Mainshaft seems to have NO endfloat adjustment in the case(that I can tell) There are lots of endfloat adjustments for the gears that ride on it. But once you get that spring clip on...that's it. That measurement is fixed. There is a distance piece in the back(#576735)...but it doesn't come in different sizes, like the others. Just one part number...one size. So it just has a fixed length, when driven into the bearing in the main case.

* Pinion has some endfloat adjustment. It's just mostly to get the little spacer between the circlip and the bearing to just...bearly...spin. There might be some adjustment here, but it feels perfect. Just rubbing, but able to spin.

* Incorrect part numbers are out of the question here. Pinion, mainshaft and 3rd/4rth Synchro are all the same for Suffix A+B+C. There literally is no other part number. Different drawings, but the part number is the same. I didn't order Suffix D (ECM plated) parts...so it's literally impossible I have the wrong parts. But, could be bad machining(not the first time).

I was thinking of rubbing down the distance piece (#576735) on the back of the mainshaft. I could adjust the fit. But I'd be guessing. I wish I had detailed measuremnts..then I could tell which part is out. Can anyone measure theirs? If you have a disassembled gearbox laying around?

1) Pinion gear end-to-gasket surface distance.
2) Lengrh of 3rd/4rt Synchro.Brass to brass.
3) Length of roller bearing.
4) Depth of the mainshaft, from gasket surface.