mega cabs are 2500's so with the gas engine it's an AAM 10.5". you can get your build sheet from dodge:

https://www.dodge.com/webselfservice/dodge/index.html

Click on the link down the left side of the page that says "Equipment List"

Enter your VIN in the smaller search bar and click search

Codes:
[DME]=Axle Ratio - 3.73
[DMF]=Axle Ratio - 4.10
[DRW]=Axle - Rear,10.50
[DSA]=Axle - Anti-Spin Differential