I have the original OEM ECM from my 2001 K2500. Selling my 2002 K2500 without the custom ECM, need to remove it.

Had truck in for service last week, asked tech to swap in the 2001 ECM, update VIN and flash to 2002 programming. He attempted to do this, but reports a failure when it "gets to the anti-theft programming" which must not have been supported on the 2001 ECM.

Question - I never tried (or asked) to simply swap the stock 2001 ECM 'as-is' into the 2002. Does the VIN have to match the 2002 truck to work, or could this work, if I simply leave the stock OEM 2001 programming in place for the 2002 truck?