Didn't GMC run some BIG inline sixes in their over-the-road tractors back in the early 50's? My uncle ran a big gas-engine tractor that had been retired from one of the local trucking companies back in the late 50's to haul the big boats he repaired. I can't remember much about it, other than it had a crash-box 4 or 5-speed trans and had to be double-clutched between every gear. It was a single-screw rig, with vacuum-over-hydraulic brakes, I think.
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!