How much weight are you pushing? How much HP do you want?
The list of motors, with AL heads, at a minimum, from 2.0-3.0 liters, that will put out 150-250 hp is endless (what that 304 puts out). Not sure what it puts out, but in the late 70s, power went to nothing in American cars. A 305 Chevy sometimes put out about 165HP. That is, carbureted, electronic ignition (Non-Computer) motors. You can find AL blocked Hondas, Nissans, Mitsubishis, and Subarus. But, the possibility of you needed to wire in a computer is more, way more.
Both motors (computer controlled vs carbed have their benefits).
My guess is that a 304 V8 would have a pretty good re-sale as it will bolt right up in a CJ.
Talk to Kennedy, start watching Craigslist for wrecks, buy the whole thing and recycle the rest. You'll get a radiator and fans w/it.