Loved the pics of your Ford so much I had to buy one of my own.
Actually I came up with this one off a auction a couple weeks ago, and to be honest, I thought I was going to bring it home, part it out for motor, trans, and rears, and scrap the rest. I drove about four hours north of my place, looked the truck over a little (I purchased it online from pictures) and drove it home.
Its a Cummins 350 with a 13sp trans. I'm not sure what rears are in it- they must be like a 3.73 or 4.11 or so b/c I hit close to 70 on the way home. Its a spring suspension over a walking beam, and when I left the quarry where I picked it up, I thought it was going to take out all my teeth it rode so rough. I think the tires were flat spotted from sitting, and the rubber bushings in the walking beam were froze up. About 30 miles down the road, it started to free up and ride smoother. The closer I got to home, the better it rode. That's when I got close to 70 down a good hill, in the flats it would run a smooth 60-65.
It ran so good on the way home, I hate to start cutting it up for parts. Its double framed, and has had several different set ups in its life. Its got air hook ups behind the cab, so it once had a 5th wheel. It was also a dump, its got a tower in the cab and brackets on the rear. This last set up as a winch truck has been on it a little while though, and I actually think the truck hasn't seen a lot of miles. The odometer reads 222,000 and I don't think its rolled the million mark. It looked to me like it was just the quarrys fix up, rescue, and drag stuff around winch truck. It was recently plated and inspected also.
I love your aluminum steers and how nice your dump looks, I don't know if that will be in this trucks future.