Grandpa's 66 GMC SWB

[jrbynf]

My transmission is the tko 600 with 0.6 overdrive. This is mated to a 3.7 ford rear end. This places me cruising at 70mph at about 1900 rpm. I am typically pulling about 15 inches of vacuum on level ground. At idle I pull about 19. I think the truck would have done better with this steep overdrive if I would have gone with the 4.11 rear end. This would have made the overdrive more useable in the city, allowed easier starts to protect the clutch when towing, and placed the Rpms more in the powerband. I am no expert but have done a lot of research on these topics to build this truck.