If they plug an OBD2 connector to read the car, then you want the vin to match. PCM would need to be updated.
And the BCS plug and now the wire for the perf shift. Anyone read what I write?
It'll run off the 98. Can't pass a plugged in test though based on incorrect vin. Trans tables will be wrong, as will the fueling and timing and cylinder airmass and a bunch of other things.
It'll start on the 99.. but I wouldn't do anything beyond a test start on that pcm.