Its In The Details!
Not enough time right now to list them all.
Check for missing pilot sleeves on the back of the engine, these control alignment.
Pilot installation, numbers face the trans.
Hot spots in flywheels, can't be ground out, we have the test data, causes high spots = chatter.
Watch the fork position, it can be installed flipped.
USE PATIENTCE installing trans, NO force, use finesse.
Clean the input shaft and use a scotch brite type pad to get into the splines and clean it thouroughly.
Make sure the T. O. B. bore is completely greased, pack the groove.
NO IMPACT GUN ON COVER BOLTS, GOT IT! Tighten in diagonal pattern, 1/2 turn at a time.