Each year had unique tail lights (and back-up lights), and finish panels on the trunk lid.
Each year had unique grills. 67 and 68 are interchangable, 69 is not.
67 had no marker lights, 68 round and 69 rectangular.
67 and 68 had the same hood with unique inserts. The 68's also had the engine displacement called out when the car was a formula S (i.e. cars with 340's or 383's) in the insert.
69 has a completely different hood and front filler panel to match. The hood didn't have inserts but optionally could have had two small scoops.
Don't know what the rules are but if you can only run the engines offered for that given year I would think they would use the VIN to determine the year an not subtle trim differences.