In '53 3/4 tons, the two are pretty much identical from the motor back. Sheet metal's already been mentioned. GMC is 6V positive ground and Chevy negative ground. The longer full pressure oiling of the GMC inline six the biggest difference overall. The oil press gauge in the GMC will go to 60 psi; the ammeter reads -50 | 50+ where Chevy is C or D, but speedo and temp gauge are identical. You have lots of options on the 3/4 ton rims depending on what you want to do with it for look. On my '51 3/4 ton, I had the original rims centers cut and new outer rims welded on that moved me from 15" two piece rims to 16" tubeless rims but I kept the original hubcaps. I upgraded that to a 302 GMC inline and A833 OD and it's very comfortable on the road at 65-75. Added a front sway bar and radial tires along with Juliano's 3 point seat belts Still 6V + ground and it runs great. Have driven it from Boston to San Francisco and back so it's a highway runner.

http://www.oldgmctrucks.com