you would have to find a way to put an 01+ ECM/PCM in your car...which i'm pretty sure is not possible. the immobilizer system works in conjunction with the ECM/PCM and the fuel system.

you can buy aftermarket immobilizer type systems, but they are significantly less secure than the factory installed version. i don't know of any that use an in-key transponder either...they all have little keychain devices similar to a mobil speedpass.