There are several model changes in the CJ line up... some of the major ones happening in the 70s so be sure of what your looking at. Early CJ5s (pre-say-76?) have a simpler windshield latch mechanism while the later ones use a more stable screw in knob. Sounds odd but that is an easy identifier. There are a lot of differences between the early and late versions, from frames and axles, engines, trannys, t-cases, on through to body components. Your best bet if your serious about a jeep, this one or another) is to go to a bookstore while they still exhist and look for a copy of the Jeep owners Bible by Moses Ludel. The first section does a good job on model descriptions and breakdowns. To be honest...I would avoid the early model unless you just wanted something to putter around town with. The brakes and steering SUCK! The tranny may be one of the ones no longer supported with parts (T-86AA) and while the Buick V6 is a good engine it won't win many races. The other thing is there is far mor aftermarket support for the later ones since 76 and newer (ish) share most mechanical and body parts with their longer brothers the 7 and the 8. There are no "perfect" model years... they all have pluses and minuses depending on your intended use. If you have any specific questions feel free to ask me, I may know. I've been doing this a while...lol!
