As far as I know they are the same exactly. A3A was the later production of the model year vs the A3. This era was when things were changed mid year to satisfy tightening rules for safety and emissions, but I don't believe either effected the A3/A3A.
There were guys that believed the A3A was Canadian, and A3 was USA, but this is not correct. I have an A3A from USA I've owned for 40yrs.
321,000 miles on KZ's that I can remember. Not going to see any more.