I for one, like your thoughts. Don't worry about that Faulkner fella, he likes to be the devils advocate. lol
If I'm not mistaken, the same class single axle dump truck would have used the same cab, but, the front fenders were different to cover the tires.
Ideally, I think you would want the lighter class suspension of the pickup unless you could find a buss that was air ride. Regardless, the trans, rear, extra weight, will all do their part to make your pickup feel like the cab is setting on a bus frame.
My cousin ran DT466 all the time. Still has the original D-466 in his TD12 Dresser Dozer. Dang nice machine for an eary 80's model.
Someone is doing a DT466 swap on here somewhere. IMHO, get you an old state truck or bus real cheap and swap that DT into the pickup..
Now, that being said, an old 12 valve cummins will fit easier, be lighter, more powerful, and you can run an Allison behine it as well.