I had a chevy 307 (maybe the same as your engine?) with a AX 15 Gearbox in my YJ.
It wasn´t that bad even for offroading though you have to modify at least your cooling system and your tranny.
I was running the original cooler from the 258 and it was way too small. Second problem ist your gearbox. If you have an 4 zyl. your Jeep is running the AX5 and don´t think it can stand the torque of an V8.
Think about changing these parts and you can have a lot of fun.
[B]YJ ´87 ...planned: Chevy 350, TH 400, Dana 300 twinstick 4:1
...more to come...[/B]