My bro has an 82 CJ5, when he bought it it was down on power.(Number 3 was toast) He drove it for a while and decided he wanted to swap out the old Iron Duke. A GM SB is a direct swap, but who knows how long that will last. The 4.0L is doable but then you need a new trans. He/we ended up getting a Autozone re-man ($700), added a header, intake and performace 2bbl instead of that cappppppy emissions junk carb and the thing runs good. I guess if you wanted a few extra ponies you could upgrade the cam.