I have an AMC 360 that I know needs some work done to the heads and might need an entire rebuild and a friend that has offered to sell me a 304 cheap that "ran before he tore it apart" and I am trying to decide which would be the best to rebuild and put in my '72 cj5.
I am curious if anybody has any idea what the difference would be in rebuild cost, power, and gas mileage between the two?

I have an mc2100 carb and T-15 transmisison.
Also would I have to switch out the bellhousing or any of the drivetrain to hook up the 304 instead of the 360?

The heads can't be swapped between the two can they?