What you have pictured is the standard seat belt buckle for '68. Both the base interior and "Deluxe Interior" came with these buckles. The deluxe seatbelts were a separate option available with any interior. So, your seatbelts are "correct", but you could upgrade them if you wanted to. The custom deluxe buckles were bright silver (not sure if chrome or brushed/polished) and not black like yours. Hope this helps!