I recently built a Muncie/BW R10 overdrive for a guy in New Zealand. I installed the HD close ratio gear set (Corvette/Pontiac) which has better ratios than the standard set up. He is using it in a 65 C-20 with an overhead camper. He upgraded the engine to a 350 and retained the corporate 4.57:1 rear end. It works well with that combination.
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