I like my magnum 5.9 . If you can do your own work you should be able to do this swap for less then a grand out of pocket after selling the old 4 banger and trans. I used a 46re out of a 99 ram, but the easiest trans to use is a 44re or 46re out of a zj with a v8 due to the starter being on the passenger side. The ax15 is another good trans but you will need a bell housing from a v6 dakota. I think the auto is the best for strength and offroad myself!
After selling my 4.0 I had about $600.00 into my swap.