You won't have any trouble using that OD trans with a 327 in a 3/4 ton. I had a 66 C-20 with that combination that I drove for 17 years. I Hauled a camper and everything else. I installed a 350 in my 56 3100 10 years ago and it uses the same OD trans with virtually no problems. I recommend using the relay, govenor, & kick down switch as the factory designed it.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine