Like a lot of parts, 68-72 interchange. I put a set out of a 69 Camino in my 70SS Chevelle, fits perfect. Z-bar is the same on small and big block on those years. I believe earlier years used different linkage for small and big block.
Ron
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70 Chevelle SS396, 71 Z28-RS, 95 Z28 Convertible. Aces 3081, TC #54 Gold