My 69 camaro coupe came standard with non ribbed rear brake drums. Would like to know if I could use ribbed rear brake drums from a 1968 camaro. They are both 9 1/2 inch diamiter if anyone knows for syre please let me know. Thanks Steve

they must be from different manufacturer but will fit 67-69 all same.

The ribbed rear drums must be from a later model car. All three 1st gen years had smooth rear drums. If both the diameter and depth/contact area are the same between the two types, they'll work fine.