1- I would say that you would want an ecu from a 2wd truck, espacially if the engine came from a truck with the Autotrac t-case. An aftermarket standalone ecu would be even better. 2-yes, the trans gets its shift signals from the ecu. 3 I'm certain that the ecu can be re-flashed fith the parameters for either engien, but one from a 5.7 will be much more common to find. 4 you can go carburated, if you don't want to fool with the electronics. You will need the Vortec specific manifold (the ports are different) and a dizzy that doesn't need a computer to run.
