Well the heater is a direct bolt in. Some say that you will have to enlarge a hole in the tub for the fan motor plug. We didnt have to do that, ours bolted up perfectly. You will have to modify the cowl area to accept the CJ defrost duct.
This is the finished product. We measured out, from that center bolt, one foot in both directions. We then cut that section out, and replaced it with the exact same section cut out of the old CJ tub.
If you look really closely at the picture you can see where it was welded. The cowl didnt warp at all when we welded it because we used a lot of clamps, and tacked it in slowly, also the bend of the cowl itself resists warping.