I also wonder why more trucks haven't adopted the unibody construction. It seems silly to separate the cab and body. After all, cars don't have separate passenger and trunk sections. What's good for the goose is good for the gander, right?
As an aside, I hauled 2 yards of river rock in my "3/4 ton" truck last week. I knew it was a big load because the front end wanted to wander more than usual. The trailer with 3 yards of bark dust might have had something to do with that also. From what I'm reading, I had somewhere around 6,000 pounds loaded on the axles of my truck in addition to the truck's 7,000 pound weight... and I thought maybe I could do 3 yards of rock