Hi,66Sub! I had a '65 G.M.C. 3/4-ton Camper special,equipped with a 305E V-6,and a 2-speed "Slushbox" Tranny. It also had a 4:11 posi. rear-end. Even with the 16.5 tires,top speed was 55,and that was FLOORED. Bigger trucks could achieve a little better speed with the use of a 5-speed O.D.,or an auxy. transmission.