so im looking to use a junkyard ecm (04 blue/green) in my foxbody swap project.

id like to use a 03/truck file as my base file and add 3 bar os.

i have no idea what vin or file is on the ecm, will the vin change to what ever file i use or is it held in the ecm?

can i / or do i need to match the vin in the ecm to match the file and will it cost me more credits?