Bolt in or minor modification -
Front -
High Pinion dana 30 with 1-peice shafts might be an upgrade for some XJ's
Rubicon dana 44 is basically bolt in
Waggy dana 44 is stock width but not bolt in
Rear -
Chrysler 8.25" (29 spline) and XJ dana 44 might be an upgrade for some XJ's
Ford 8.8" from an explorer. Later years have larger shafts and disk brakes (I'm going to go to the pick-a-part sunday to help get one of these for a friends TJ)
Ford 9" from some cars, not the F150. Although most are weaker 28 spline.
Common upgrades for custom and full width builds -
Front -
d44, d50, jk44, d60, rockwells
Rear -
d44, d60, d70, c9.25, sterling 10.25, 14 bolt, rockwells, etc