Here's clear pics of many common axles so that you can tell for sure:
http://www.xjjeeps.com/tech_referenc...section=2&ID=3
The Dana 44 was only in some 87-89 Cherokees with the towing package. Did not come from the factory in '91.
Also, if you are planning on hanging onto this Jeep for a while and modifying it, buy this:
http://www.ericsxj.com/book.htm
I picked it up a few months ago and read it cover to cover in a few days. TONS of good info in there.
- Justin