At least that gives you factory pieces to use. Probably best to use what was available that year to make it as straightforward as possible. Issue you may run into is the Allison; is it electronically controlled or a good old fashioned mechanical hydraulic? Will need all kinds of harness, the PCM, diesel cluster, the ability to flash VIN to different modules so that they will talk to each other, non FBW pedal assembly (unless the 08 diesel was a FBW, may need a different assembly). The biggest hurdle here is understanding how the different computer modules are interconnected and dependent on their communications just get the engine to fire lol. The vehicle I referenced before was a PCI bus truck, bit easier to mess with electrically that a CAN bus (which is what yours is). This is why you generally don't see many if at all swaps for Mopar vehicles made after 2005 (general migration to CAN bus systems). The exception here is engines within the same family, like 5.7 to 6.4.
