How can I determine the year of an engine
 

Is there I.D. numbers on 12A engines that determine the year the engine is? I have three engines that came with my 1983 RX 7 but I don't know if any are the same year or not. I want to run an aluminum flywheel because it's a road racer car. 83 to 85 they don't make the counter weight anymore that you need for an aluminum flywheel so you have to have everything rebalanced so after the cost of the parts and to have it balanced it cost over $1000. So I hope one of these engines are a 86 or newer.

just a heads up that no 1986 or newer engine would be a 12A.
The engines do not have a serial number on them.Just distinguishing features that would tell whether it was a 12A or 13b,etc.4 or 6 port..