Attached is what I'm seeing for quarter panel part numbers. Jim is spot on regarding the 63 for fastback, 65 for hardtop, and 76 for convertible body style. However, I'm not coming up with the part numbers he listed. Perhaps he was just putting examples out there - one is coming back as a "panel - cowl trim" and another has no record.
This particular page of the MPC is dated October 67 and obviously does not account for the reflector change.
The May 1975 MPC includes the "before" and "after" 2/15/1968 versions that account for the change in the depression for the reflector. The three "after" versions were the same part number as listed in the attachment, but have a -B suffix.
The initial variations was 3, one per body style. The resulting number of variations is 6, two per body style.
Finally, the 75 MPC states that the right hand convertible late (from 2/15/68) panel was not replaced as of March 1974. Strange.