True, Check out what this guy says. I once owned a 1948 Willys jeep. The guy I bought it from, put a Chevy 283 V8 in it. The original 4 cylinder Flathead horse power rear springs just could not handle the V8 torque. The pinion bearings prematurely wore out because the axle would whip so bad.
"I want to keep the truck stock with the 3-column shifter, but make it better for cruising highways."
I can cruise highways all day in my 1954 Suburban at 65 mph with the 3.55 Ring & Pinion conversion (enclosed drive shaft) and 31.5" diameter radial truck tires (about 2500 RPM). This has worked fine with the original 3-speed and 4-speed.
If I wanted an OD, I'd go with Tommy's recommendation - SM319 and suitable rear end. I think that is what Cletis has, and one of my neighbor's has that in his 1953 1/2 ton panel. It is is nice set-up.