the 2 and 4 wheel drive trannies are the same other then the tail section so they are both ax4s,the ax5 is also the same except it has a 5th gear.
Also keep in mind that you most likely have 3.55 gears so if you want bigger tires or a 5spd your gonna want to change gear ratios. The easy way is to find a 2.5l w/5spd and take both axles as they would have 4.10 gears,if you want real big tires you will most likely have to spend some money and regear the axles(I'm going 4.88 with mine),once you have the trans,tcase,and axle only other big thing is drive lines.