In the 2500HD trucks, the Dmax/Allison combo is only available with the 3.73s (unless something has changed recently.) In the 3500 trucks 4.10s are optional. In the Kodiak 4500 and up trucks you can get deeper gears (4.30s I think).
I was thinking the duallies came standard with 4.10's. Optional in the SRW's, which are standard 3.73's (3500's that is). I do know my 3500 with 3.73's has plenty of zip off the line and gets pretty decent mileage for what it is.