Now that the center diff is all reassembled, put it back in the transmission. Cool tip: Put Vaseline on the o-rings and plastic bits on the shaft. Rotate it to get it to seat right. I had to tap mine in gently to get it in all the way.
Now put the output shaft into the diff. This requires a lot of twisting back and forth to get all the gears to line up. Then it should just slide right in.
Put clutch pack in, one piece at a time:
This is what mine looked like with the entire clutch pack installed.
Here is a shim, but you may have two or three, and there will be others in other places. This one goes in the tail housing. Use Vaseline to hold it in place if it keeps falling out. Put back all shims where they belong:
Now it's in place:
Now you gently put the housing back on, being careful to keep the output shaft AWAY from hitting the oil seal. Recommended: Use a new metal gasket. I didn't, most don't need one, but risking a fluid leak is up to you if you don't want to replace it. My gasket looked fine and even, and it sealed right back up. I was able to push my housing on 95% of the way until the alignment pins hit at 1/4" inch from full mating, with just gentle taps to help it along. Do not force the cover on. Using the bolts to draw it on will crack the housing!
Once alignment pins are aligned, gently tap together with wood, hammer:
I used my electric drill on a low clutch setting to zip in all the bolts:
Then I used a torque wrench, and torqued everything exactly to spec. This is the key to getting the gasket to seal right.
Now go launch.