How do I identify the year my 12a is? I think it's 83, but I want to make sure when I get a new flywheel I get it right. I know there's a way to tell by the "I" shapes and notches on the housings, right?

 

It's really not the irons or housing your trying to match. The flywheel matches the rotating assembly (e-shaft and rotors). There are letters stamped in the well of each rotor. 83-85 will have "F" for front and "R" for rear along with an "N". All other 12A rotors will only have the "F" and "R". Also look at the flywheel. It will have a number on the side that faces the engine. 83-85 12A will have a 31 and is 26 pounds and uses a 225mm clutch disc. 81-82 12A will have a 21 and is 23 pounds and uses a 215mm clutch disc.

http://www.mazdatrix.com/faq/flywheel.htm

 

KansasCityREPU, not to take from the OP, but would it cause any harm installing an 84 clutch on an 83 engine? (I may have inadvertantly done this, and want to correct if it will hurt something, the engine is still out for the car so at least it's easy to get to)

 

just want to throw this in there, the 1983 and up 12a engine has a 2 outlet coolant passage on the drivers side under the oil dipstick and the pre 83 has one coolant passage outlet due to the 1983 and up having the top mount oil cooler.
its handy to tell without taking anything apart.

 

So it has...

-The "N" on the rotors
-Larger clutch
-Top mount oil cooler (Replacing this with a 13b oil filter pedestal, retaining the stock 79 oil cooler)

It's an 83 then right? That's what I thought.

I thought you could tell the housings and irons apart by the notches on the tops or something. One is "I" shaped and one is [] shaped like a 13b.

 

If your old flywheel has a "31" on it, then it's a '83-85 12A.

http://www.mazdatrix.com/faq/flywheel.htm

 

don't EVER rely on the flywheel unless you bought the car off the dealers lot in the early 80s always look at the engine!! the flywheel can be changed the engine would more or less not be disassembled.

Not trying to say peejay is wrong because he is not wrong but i would never rely on information from a part that attaches to the part that i need the 100% correct information on.