This is not a how two question, as I know there are hundreds or posts on that subject. This is more of a should I, which probably has multiple posts as well. Here is my situation. I have a 92 YJ with the 2.5L, and 4.10 gears. I have done a considerable amount work to this jeep, including lockers, armor, lift, modifications, lights, racks, interior, and so on. Frame and tub are in really good shape. I am overall happy with my jeep. Takes forever to get to the trail, but in 4L, pretty... YJ 2.5 to 4.0 swap