I wouldn't plan on using the axles from a 4.0/stick. they will have 3.07s. your current rear should have 3.55s, so you can keep that and grab a front from a 4.0/auto XJ from the junkyard. easy. :D
to swap to a 4.0 you will need to change pretty much everything, harness and all. a good running donor is the way to go.