GVWR at 10,000# is a cross over point. At 10,001# some states require a commercial drivers license to operate the truck. Hence the 10,000# GVWR. Some will tell you that the manufacture listed at 10,000# because there is the entire drive train just not the rear axle and tires to take into account.
My 2004 F350 has a GCVWR of 20,000# which means my 8,000# truck leaves me a tow capacity of 12,000# trailer. If you look at the numbers you can go from gas to diesel and it stays at 20,000#. You can go from 3.73 to 4.10 rear axle and it stays at 20,000# you can go from SRW to DRW and it stays at 20,000#. Move to the 2005 truck and now you get credit for all these things.
As long as you are not pushing the truck to it's limits you should be fine. I roll through PA on I-80 with my 12,000# 5er, cruise set and enjoying the view.
This is just my opinion and sales people write the brochures and legal people write the door stickers.