Richard, a 318 or a 360 are both good cheap engines to find for that truck and it depends on what you plan to do with the truck, if its just a cool little driver then the 904 will work just fine but if you plan on towing or heavy duty work from it I personally like the 727 better, they are a little stronger for that kind of work.
I have a 318/904 in my squattie truck and it has been great so far and both were used before I put them in the 40 Ron...