The Cummins and the Allison both have their own computer. They just both have to be able to talk to each other. But basically, this combination already exists. For one, take a look at a Federal Express unit. Those little milk truck look a likes. They have a Freightliner Body, Cummins Engine, and Allison Transmission. Not only that, there are many heavy duty units out there that have Cummins engines and Allison Transmissions. I'm not positive on the Cummins half of things, but on the Allison side, the computer for a larger unit is the same as the smaller units for pick-ups.

But, the one exception to this is the older hydraulic models. AT545's. They don't require any computers or wiring. Well, mostly. You still have to wire in the speedometer pickup and modulator. But these transmissions stopped being produced in 2000. You can still get them all over the place though if you know where to look.

But also, as stated before, while this is all possible. It's just not worth the price tag for the conversion.