Easiest install for a SB OD, auto trans.

Honestly, I' d get the engine and trans out of an XJ Cherokee 2wd. 4.0L., Aisin AW4 4spd. automatic.
Almost a bolt in (at least compared to a 318 and rather obese Mopar overdrive); and if you don't mind wiring, the FI isn't too bad of a swap.