The middle ports did not have washers under the bolts. The outer/end ports of the manifolds got the thick spacer washer, then a french lock, then the bolt. The tabs on the french lock were bent over the bolt hex head to prevent loosening. The order is important because you cannot properly bend the locks if the washer is in between it and the hex bolt head.
Here's pics of both the thick washers and french locks for SBC and BBs. Factory locks were steel, most repops are stainless.http://www.licorvette.com/french_locks_Corvette.htm
I can't recall exactly, but if you start adding a/c brackets etc to the manifolds you need to check your AIM to see if the french lock was still used or left off.