Matt sometimes parts were used for quite some time. The C8AE-H heads were used until mid 71 when the D2TE-AA version came out. And the D2 heads were used until 76 in production. Both were service parts for years after. My tunnelport heads carry a C7 casting number and are 71 service parts. Lots of parts on my Cougar are the same as your gas pedal. The part numbers were always upgraded in the books but in many cases the casting number on the part itself remained unchanged.