I ran a 59 flat bed 3800 with the 4.56 gears at 65-70 routinely, with no problems. Of course, it had the 18" tires, which helped a little, but the main problem is that people who are accustomed to modern engines running just above idle speed on the highway get terrified by the sound of an engine actually working for a living. Most of the sound they're hearing is coming from the fan. Get a pair of earplugs, and a pair of heavy boots. Stand on the throttle and keep up with traffic!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!