It's an inline 4, not a v4. Also, it's probably a 2.5 AMC engine from the looks of Jeep Tech Pages and the ever true wikipedia. I don't think there were any YJ Rubicons.
Anyways, the way I look at it, a YJ is a YJ. My CJ7 is some type of limited run deal, but it's just a CJ7... you know? My...