Just the torque multiplication factor would be reason enough to do the swap. The Dodge engineers quickly corrected this issue going from 04' to 05'.
2004: 1st Gear thrust in Ft. Lbs. (525 X 2.66 X 4.10 = 5,725.65)
2nd Gear thrust in Ft. Lbs. (525 X 1.78 X 4.10 = 3,831.45)
3rd Gear thrust (Gear of choice) (525 X 1.30 X 4.10 = 2,798.25)
2005: 1st Gear thrust in Ft. Lbs. (525 X 2.66 X 4.56 = 6,368.04) +642.39
2nd Gear thrust in Ft. Lbs. (525 X 1.78 X 4.56 = 4,261.32) +429.87
3rd Gear thrust (Gear of choice) (525 X 1.30 X 4.56 = 3,112.2)+313.95
This considerable increase in torque multiplication is why drivers say the truck feels "lighter". Better 0-60 times is the result.
The reason I say 3rd is "gear of choice" is this is the gear that the truck will put the smack down on most vehicles. The engines WIDE torque curve catapults this truck to high velocity, 4th is not bad either until you reach terminal velocity and our aero begins to become a disadvantage. This is right were I personally have punished my Buddies 392 Charger, plenty of C6 LS2 vetts, an Audi S8 sedan, Pontiac G8 and a few assorted sport bikes. LOL.
I would go with the no brainer for axle lubricant... Mopar 75W90 Full synthetic gear oil with Mopar limited slip additive.
Cheers!