Tech there are three 406 heads and you were correct on the cc's for the two earlier ones. Some books and guides have the cc's as all the same. The C2SE-B and C both use the 64-67 cc chambers but the C3AE-C smaller cc ones. These were pretty rare to find on the 406 and most used the C2SE versions. BTW some very good write ups you have there and very good reading!!! G.