Hate to say it, but why not just use the other software and full flash an 03+ OS into it? If its really in the PCM, that will do it. If not, then change your VIN to an 03 one and have a dealer flash the BCM. Once they flash you'll have to use that VIN otherwise I dont believe the VATS will let the engine start.
Thats a good idea but will I be able to pass the state inspection with a different Vin number?