I'll be running it behind a 99 magnum 5.9 using a 97 OBD2 harness rebuilt by Magnum Mopar and computer tuned my Flyin Ryan. I had Even at Magnum mopar leave the auto pig tails for the 518 RE trans... Just in case I locate one...
The 42RH in mine is behind a 96 mild built cammed 5.9, carbbed with pressure switches for automatic control of the electrics for OD and lockup.
Sounds like you already have a definite plan, and I was just curious.