This Dual Exhaust Kit was available for 260, 289 and 302's through 1968 (it is shown in the 1967 only MPC as well as in the 1960-68 MPC. Sometime between July 1968 and July 1969, the Part Number changed to C5ZZ-5210-B, and interestingly, during that same time period, it was then shown as "Obsolete".
Bob