since you can swap late model shafts (with the bigger ujoints) into an early CAD axle pretty easily, they are all pretty much the same up to 2000 when they switched to low pinion. but even that isn't really all that bad. every single TJ has a low pinion front and they manage pretty well. get an axle that appears to be in good shape and has 4.10s (unless you're planning on regearing)
do be sure to know what year the axle is. while all years can be swapped in, the bearings and brakes and such changed here and there.