JC-Whitney will not have what you need to make a 4x4 conversion.
Do a search for u-pullit yards near you. THe conversion is easy if you have the parts.
ALSO... live on e-bay. Axles, trannies, t-cases, and driveshafts can be had for cheap if you pay attention.
I bought a complete D-44 rear end for an XJ (cherokee) for $400.
ALso... go to
www.jeepsunlimited.com It's a lot of stuff to root through BUT they have a HUGE for sale section and chances are someone near you has parts for sale.
Here's what you'll need if you don;t know already and these parts below can come from ANY of these vehicles that have the same motor as your comanche: 1997 or newer wrangler, of course any year comanche, and any year cherokee (1984-2001). I highly recommend finding your parts from a 1996-1999 cherokee as they have the most desirable factory late model jeep front axle. ANd you'll need to be sure the donor vehicle has the same size engine... hopefully it;s not the 2. 8L V-6... but the 4. 0L and 258 (4. 2L) I-6 both have the same bolt pattern HOWEVER the 2. 5L 4 cyl has a different pattern so parts between them are not interchangeable.
4wd transmission (the 2wd trannies are different in the tailhousings)
front axle
front and rear driveshafts from the same wheelbase 4wd vehicle
transfer case
shifter for the transfer case (and cut the floor out for it to fit)