Originally Posted by t5cents
it doesnt matter that u have a 1999 with a 4.0...
Oh come on, don't you know bout how the 99 4.0 is completely different?
On a serious note, you need to know what you wanna do with it first... I'll assume that if you want a "long travel solid axle" You mean that you want a solid axle with flexy suspension with plenty of travel for playing in the rocks and trails.
Solid axle (gears/locker if necessary/wanted) (narrowed if wanted/rebuilt as needed)
steering gear in place of rack and pinion (ifs toy box is common)
Leafsprings or coils/coilovers
new wheels (unless you use a d30)
It's really not that bad.