Here is a
LINK to a Jeep forum that may be of some help. They are speaking Cherokee but I bet it holds for Comanches too. I've owned several Cherokees and Grand Cherokees. I had one with a 2.5 and a 5 speed and was impressed with what it would do. 2 had 4.0s and the present one has a V8. I like the inlines best.
If it was an earlier YJ that had a 151 GM motor I'd say jump on a 3.0-181. The 151 Jeep used had the same bell housing pattern as SBC and later L6, and the 153-181 Mercruisers. The jeep bell housing is aluminum and looks like a Ford on the trans side. It matches Mustang T5s. I don't know Jeeps that well but I have a 151 fron an'80 YJ that I have thought of putting in a Comanche. Let us know what you decide.