I have a 1990 YJ and am not satisfied with its 2.5L. I have been looking for a 4.2L to put into it but I am not sure how the wiring will work if I get a carburated engine since mine is TBI. Will I just have to rip out the computer and most of the wiring and wire it all myself? Or should I get a CJ wiring harness set? I am also not quite sure if it will mate up with my AX-5 Transmission.

If anybody has any suggestions, I would really appreciate it.

Don't worry about the computer issue. Its a paper weight anyways. I have a 90 YJ and the computer was toast. So I disconnected it and just hooked up the vaccum lines as if it was a pre 85 model. Also clean the gas tank and put a new strainer on it, sand is bad for the carb. I dont know if the engine will bolt up to the trans. The computer is junk. I live in a strict emissions county and I had it pas with flying colors! Good Luck.  

The ax5 does not bolt up to the 4.0 or 4.2 you need to change trans. also I know advance adapters does not make a adapter for this swap. I never had anyone tell me they bypassed the computer on a fuel injected model but I will now try it myself. The carb engine is the symplest way to change over. A cj wiring harness I don't think will help you. Just install the sending units off the 4 to the six but remeber if the computer (if left in) will come up will error codes because it won't see the 4 injection system anymore.