I have 1 ton and 2 ton AD trucks and I can't see that there is any more room under the hood and between the frame in one or the other.

The larger fenders on the (1.5 and) 2 ton are all about fitting larger tires, not engines.
The shallower hood on the big truck is because the fenders are taller.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-