I am restoring a 1966 SS to original.which brake drums are correct,finned or non-finned,this car has one of each on the rear.Thanks Bob

Non-finned on all 4 wheels. The front drums became finned for: 1968 Chevelle SS396s, all 1968 wagons, 1968 Chevelle L-79s (327 325-horse), 1968 Chevelle L-30 (327 275-horse) when equipped with 4-speeds, 1968 Chevelle L-30 (327 275 & 250-horse) convertibles and Sport Sedans with a/c.

I believe finned rear drums came online for 1969 (of course the SS396 came with standard front disks starting in '69).

Cam , thanks for the info.now I only need to find a non-finned drum which should't be a problem.
Bob