All Jeep inline 6 cyl bellhousing '72 up (except a few leftover Postal Jeeps with the starter on the LH side) are the same as the 304, 360, 390, 401 (I think 287 and 343 as well) but you have to watch the crankshaft flange. '71 and older are set up to fit Borg Warner auto and T96 trans with a small clutch and bell housing.
My '83 J10 longbed had a T5 (it's only good for parts since it was run low on oil) behind the 4.2L, but they aren't strong enough for a V8.
The 2.5L (84 up) inline 4 is the same as the GM 2.8 V6 used '84 to '86.