The last year for that option from the factory was 1967. GM placed all future bets on disk brakes. Of course there's nothing stopping you (no pun intended) from running with Kevlar brake shoes from Praise Dyno Inc. or sinistered metallic brake shoes on your car if it is a '70 with drums. They are more or less the same 9.5" drums be it a '70 or a '67 (cooling fins on the later drums).