These trucks were designed for the rural roads and farms that existed before Eisenhower's interstate system. 45-50mph was a pretty good pace and beyond 65mph was usually the domain of V8s. For me, a great deal of the charm of driving an old truck is the smell, sounds and limitations of originality. If you are going to stay original, I suggest you enjoy the back roads at a leisurely pace as these trucks were designed for. I keep a motorcycle in the garage for those occasions I feel the need for speed.
RdsLessTaken/Don

Backroads Drive:
http://s1291.photobucket.com/user/RdLessTaken/media/IMG_85131_zpsd8f0ffba.jpg.html