TRE spool

If you run a spool center diff, the rear end will hop in tighter turns. If you dont mind that it should be ok.

As far as changing it while its in the car, you have to remove the pass. side case of the tranny, the viscous coupler (with tough snap ring pliers), then remove the 5th gear fork and synchro (gotta use a punch to get the pin out of the shift fork). then a 31 or 32 mm socket to remove the two big nuts in order to remove 5th gear and the other gear (i forget what it is). then the next layer of the case will pull off. from there you can remove the center diff. (carefull though, there is a tiny ball bearing you need to save to put back in).

as far as a welded VC... you can get a VC eliminator from tre for pretty cheap too.. mabye just go that route.

for pics and such look on vfaq.com there is a good write up there on a rebuild that will basically show you what you will see inside.

good luck!

j