More on the C-80. Check out this video that is indicating the new '62 Tandem Axle Dump has a 409. Having a 409 would make it a C-80, but check out the picture on the YouTube video as well as the truck at the 1:04 mark, I'm not seeing a Straight Front Axle. The '62 GMC 6500 was the first year for it in the '60 to '66 trucks and I believe the '62 C-80 followed suit.
Edit: I dug a little deeper and it looks like the Straight Front Axle was an Option for the C-80 in '62.
Also note the mention of the 4-53 Detroit available in the Mediums: