These transmissions are really picky...try reading some of the posts in the tranny forum.
But over all, syncros like to go bad (3rd and 4th mainly) and the differentials too, as well as the shifter forks.
There is a spacific FAQ at the top of the tranny forum that list the parts and partnumbers you need for a sucessful rebuild.
But over all i am not surprised your rebuilding it again.
I had mine rebuilt by terry haines in Michigan. has gone 40,000 miles no problmes.
secondline@ameritec.net (might be .com) is his e-mail...he cosed me 1300 for a full rebuild (including shipping).
PM some local CEGers in your area too...they may be able to help with your install.
Lupe