[JustinOK]

Also, you can find out which engine came with the vehicle based off the vin#.

fourth character.

X is 6.2 NA
Y is 6.5 NA
Z is 6.5 TD
D is gas
F is 6.5 TD heavy block
P is 6.6 Duramax

Have a dealer run the vin to see if there was an engine swap though, as the vin# would not change.