Drove a new GMC 366/4bbl/dual exhaust/5-speed 26' box truck back in the late 70's.
Was fun-would easily 'take' a few cars off a light. On e-way no problem getting up to 70 then it would back down to 65 (governor). Most of the time it was lightly loaded. Ran way stronger than similar 90's Ford 370/2bbl/5-speed.