I used the same tailhousing....just pressed in a new bushing that fits the 28 spline shaft.
If the other parts are good, I wouldn't go to the trouble of going with the big stuff. If you do go with a 31 spline output, you will have to find a 31 spline tailhousing to fit it. So that will be more money on top of everything else. David Kee said that you could bore out a 28 spline tailhousing...but I'd have to send it to him to have it done.
If your mechanical skills are good, then you should consider doing it yourself. You'll save quite a bit of money. I got an excellent deal on my tranny.......but with all the rebuild parts I've got a hair less than $700 in mine.
