All the parts are there for the conversion
The part on Ebay is the whole carrier; the limited
slip part is inside along with the spider gears.
Just remove the old carrier, remove the ring gear
from your old (non-posi) carrier (usually the ring
gear bolts are reverse threaded, meaning to remove
them, turn them clockwise). I'd reference a good
shop manual on Dana 80's for more info. The
carrier bearings need to be pressed on with a
hydraulic press (easy to find and do this). Then
install the unit back in the housing. It is a good
idea to check the gear face contact pattern with
"prussian blue" to make sure the setup is right
so the gears wear correctly and don't whine. If
you are not changing the gear ratio, the pinion
gear, which is the smaller gear that is driven by
the driveshaft, pinion depth need not be changed
so there is generally no need to re-shim to get
the right runout.
General consensus here is that the limited slip
that is installed in our trucks is marginal, and
some are set up tighter than others. It is by no
means a "locking" diff setup. I really like the
Eaton brand of Locking differentials. They are
both a limited slip and positive locking diff.
GM uses the Eaton in their pickups etc. Good unit.
Unfortunately Eaton does not offer one for a Dana.
If you want a good locker for the Dana 80, talk
to Okie. He has a lot of experience there. I can't
remember what he has in his truck right now.
The stock limited slip (like the one on Ebay) is
definitely better than no LSD at all.
-Chris