You have to replace the case and add the locker gear carrier and shift
fork to the innards along with adding the servo and bracketry and vac
lines and switch and.....to the outside.
 It CAN be done by those of you who are comfortable rebuilding a trans.
and have some special tools, but otherwise don't try this at home.
 In round numbers, the stuff costs about $500 (parts only) plus the servo
& external stuff which are available by me or Derek Drew...I only have
enough to do 2 or 3 of them.
Haven't had time to check the link that Jim Arnott sent me, but have been
told previously that no limited slip is available.
Daryl of AA Transaxle
Duvall, WA. (Seattle area)
(425) 788-4070
1-877-377-0773 (toll free)
aatransaxle.com (web site)