I have iinstalled a few new or rebuilt computers. Either way, the replacement ECM s has been reprogrammed to include the VIN and actual mileage on the vehicle, to comply with Federal laws primarily pertaining to speedometer tampering.
The reprogramming is done by the rebuilder or by Mopar.
Technically, without reprogramming, replacing the computer is a Federal and possibly a state violation.
Here in California, during smog inspections, the computer must match the actual VIN and the mileage ( the mileage must be greater than the previous inspection). The vehicle is connected, through the OBDII port, to the state data base, so it is difficult or impossible to fake it.
You are lucky to have counties with no inspection requirements, if this becomes a problem.
Let us know how it works.