If he has the ford motor sitting around it might be worth putting in. If he has to buy one it would be a lot simpler to get one of the jeep 8's and put one of those in. He will probably have to have an adapter to hook up the ford engine and to a jeep tranmission and if he used the ford tranmission I do believe he would have to change the tail stock to make it compatible to a transfercase for 4wd. It would be a waste to change from a 4wd to a 2wd jeep. Good luck.
1978 CJ7, frame off rebuild, NV3550, Dana 300(twin stick with a sight tube), I6(258), Dana 44 Scout Axles with 4.09 gears, truetrac LSD. The rest yet to be decided.