Substantially higher numbers than the 1500 yet it is only .4 of a second quicker? Although the Chevy is a heavier truck.
The Chevy is almost 1600 lbs more, most crew cab 1/2 tons are about 6,000lbs, and only running through a 6 speed transmission as opposed to an 8 speed. I would imagine the 8 speed does a much better job of keeping a diesel in it's optimum torque range.
But yeah, 7.5 is probably optimistic for a 0-60 time.