Other years may interchange besides what Kawasaki says but the issue will be the exhaust valves.
You will need the exhaust valves from whatever cylinder you decide to try.
CYLINDER 1542 FITS 88 KX250 11005-1542 BORE 66.40 STROKE 70MM
EXHAUST VALVE CENTER FITS 88 KX250 - 12005-1116
EXHAUST VALVE LEFT FITS 88-89 KX250 - 12005-1099
EXHAUST VALVE RIGHT FITS 88-89 KX250 - 12005-1100
A bad port job can be welded up and re-ported...