Your axle weights are posted on the same door sticker that lists your GVWR. It will list a FAWR and a RAWR. These will add up to more than your GVWR. Additionally, many trucks, Ford especially, base the axle weight on the weight rating of the factory installed tires. The actual axle assembly might be the same one used in a heavier duty truck and rated for more weight with higher rated tires.
The axle in my Chevy, an AAM 11.5" is rated by AAM at 10,000 pounds. Chevy only gives me a RAWR of 8,500. I usually run between 8,500 and 9,000 with camper, boat, family, gear, etc. all loaded.
To answer the diesel vs. gas weight question another way:
With my diesel powered truck, fully loaded I'm about 2,000 pounds over the GVWR but I'm about 500 pounds under the front axle weight rating. All the weight is on the back axle. If I had a gas engine I would probably be 1,000 pounds under my FAWR but still over the GVWR.
I'd love to carry more of the weight on the front axle but there's no way to move any more forward.