Swap pluses n minus 4.2 with 4.0 head n TBI or GM 4.3 n TBI

[smithjw1970]

New to the forum. I just bought a 1988 YJ 4.2 and am amazed at the lack of higher end power and poor mileage. Since I am a consummate tinkerer, I can't let it stay this way. Besides this it runs and starts great and i m falling for it a little bit more each day. I am a muscle car big block fan and therfore cant leave it alone. I just did some research and sourced two swap options and wanted to get some feedback on what is better and the best bang for the buck.

Option 1 - convert it to the 4.0 head, TBI, and fuel/engine management system. I have already sourced the donor, it runs and has only 145K on the head.

Option 2 - GM 4.3 swap including TBI and fuel/engine management system. I have already sourced a rebuilt engine with 40K on it.

Goal is better fuel mileage and power. Less for 4x4, but still needs to be a factor.



Thanks and great forum
Jason
Please reply with experience and fact/resources I can use soon as I move quickly.

[gopbobby]

Which option did you go with?