the 1996 "black box" PCM is inferior to the 2002 "0411" PCM that should be factory installed in your van. keep the PCM you have and wire & program your conversion as if it were a 2002 Express/Savana van - the Vortec 5.7 V8 was an option in these vans and uses the same PCM as yours. if your silverado upper intake plenum looks like this :
then i believe the stars have aligned for you!
then i believe the stars have aligned for you!