any way to tell what CID it is

On the driver's side on the top of the waterpump area of the block... Just in front of the flat bar that holds the intake gasket down... Is there a rectangular pad? If there is a pad, it's RB, and you can scrape the pad to see what's stamped in it as mentionned. If there's no pad, it's a B, and the stampings are on a flat surface hidden under the distributor.