The AMC 360 fits in w/out a problem. Keep the D300 T-case as it is geared lower than the 20 and strong if not stronger than the 20. Keep the I-6 ignition control module. Not sure on motor mounts but at the most you would need to change the passenger side? Get the mounts from a CJ with a V-8 and they will work. Pull x-tra brackets for the air-pump as these break and keep the factory A/C from a wagoneer 360 to use for compressed air. I would go with an NP435 or NV4500($$) for a tranny and get the advanced adapters kit for the tranny. Of course a T-18 works as well.
1977 CJ-7, D44 corp 20 detroits, D300, NP435, 304, 4" BDS, shackle reversal, 33X12.5 BFG MT's