Another interesting difference between the 1/2- and 3/4-ton trucks is the way the frame is designed. On a 1/2-ton Chevy the width of the frame inceases until just behind the rear axle. On the 3/4-ton the rails are parallel starting under the cab.
Canadian GMC's of the Advance Design/New Design era ran Chevy motors. I suspect that is part of the confusion above, since we have at least one Canadian in this dialog.
I too have never understood why GMC sold a long box 1/2-ton and Chevy did not. The suggestion that it has something to do with the better GMC motors doesn't make sense since as far as I know Chevy ran the same 216 in 3/4- and 1-ton trucks.
I suspect it was some marketing decision rather than one made based on some engineering issue.
