DONALD - Guess I've had to WALK home or call for a ride when my little Cum-a-Parts couldn't make the trip. Most cases actually due to the company's lack of maintenance than design problems with the engines themselves. There were several times where I had to hunt up a shop 500-600 miles from home to get repairs done, almost missing pickups, etc.
My Cousin & His Son used to pull their Dodge 4WD P/U's in local truck pulls. Not sure what actually happened but my Cousin had the crankshaft break in his 5.9L. He also used it to pull a BIG 5th wheel livestock trailer every day so it didn't owe him much.
Years ago when I was driving it took 855 or 903 CID to make 300 HP, now they can make 350-400 HP with 359 or 408 CID. But towing 75,000-80,000 pounds with 300 HP you have to drive FLAT-FOOTED", and use all the gears you have.
Because of the way I spec'd my '96 F250 out, manual 5-spd & 3.55 gears it's only rated to 16,000# gross, truck, trailer, cargo & passengers. But with 4.10's & the 4-spd E4OD auto it would be rated 20,000#. When I hauled Dad's '51 M here four yrs ago I "Axled-out" the truck & trailer on a free BIG truck scale. I had WAY too much tongue weight where I had the tractor tied down the first time, soon as SON & I parked the truck/trailer We moved the tractor BACK about 4 inches and it was PERFECT according to the scale, and it pulled MUCH better. I have pic's someplace of the truck/trailer sitting on the scale and you can see the readout @ 16,800 or so without SON & I in the truck, so we were about 17,300# on the road. Even stock I could accelerate up hills without problem. The Interstate entrance ramp I got onto I-80 at was uphill for over a half mile and I was doing 65 by the top of the hill. It was TOO much fun listening to the turbo whistle thru the straight pipe or I might have been able to get better MPG's.