depending on the 4b you go with it would be nearly plug and play if you were to use the trans/engine harness and PCM from a donor cummins truck.
With a p-pumped 4b, your literally plug and play, right down to using the accessories from the 6b (alt, ac pump, power steering, ect)
As for the fuel pump, the gasser uses an in-tank electric. the cummins uses a block mounted mechanical pump. you can gut the factory sending unit and make it just a pick up tube, or you can swap in one from a diesel if you can get your hands on one.
Its all the little stuff like this that makes it MUCH easier to have a donor truck to rob the parts from! even if it is a rolled truck with a blown engine!