There is a guy over on OldGMCTrucks who swapped a Cummins into a 1-ton. Nice swap BUT he had to cut into the firewall and passenger compartment to make the motor fit. I suspect it puts a lot of heat into the passenger compartment, so while it might look and sound cool, being in it might not be so cool.
Grigg went with a four cylinder Diesel. I don't remember if he has said why, but length may be part of his reasoning.