I'd get a waggy centered rear axle to match the waggy front axle both being 6 lug and front the same vehicle would be nice. Also a non disco front housing would be better still.
The rare XJ rear dana 44 can go for a pretty penny and $300 in stock form is fair for it. Is this for your ZJ? With having to mount the brackets for the ZJ and the waggy and XJ 44 having drum brakes...I'd suggest pulling a easily had 95-01' Ford Explorer 8.8 which comes with the 5 on 4.5 bolt pattern as your front dana 30 and is stronger than a dana 44 and has nice disc brakes too.
A waggy front axle would be nice tho so you get the manual hubs.
Just depends on what your plans are for your rig and if you plan a all out wheeler or dd/weekend warrior build.