wallaceracing.com has a lookup where you can check those codes (16, WZ) for performance specs. Yes, the other number is a sequence number and would match the Billing History for the VIN that is stamped on the lower front of the engine, along side the timing cover.

Here is a Firebird engine application chart for '68.

http://thefirstgensite.com/library/engines/68birdengines.jpg