2007 isx cm870... PLZ HELP

[Chamberpains]

The ECM will have the original Engine Serial Number on it. It has a sticker on the front and also it's often stamped in the back side of it. You can register that engine number in Cummins Quickserve and it'll tell you the original truck that engine was put in. That doesn't do any good for what engine you have in the truck currently. You need to track down what serial number they installed. Maybe call the place that installed it and see if they recorded it somewhere or maybe they know or can track down the VIN# of the truck it came out of. Then you can call a dealership and get the Engine Serial Number for hopefully that engine.
As far as the mileage matching, they can offset the mileage in the ECM to whatever they choose using Insite.