So just judging by the picture if you truly want to go back to original. This is what I notice:
You would need to
-replace ZL-2 hood with a flat hood
-remove the white Z/28 stripes,
-add the black vinyl top and trim
-remove the spoiler(s)
-if the wheels are original then add the 67 (smaller) rally cap. (wheels should be 14x5 code B, or optional 14x6 code FC)
*may want to check if the antenna is original, looks bent back in the pic like it may be aftermarket.
Oh and make sure to have fun while making your changes!