Auto Trans. help PLEASE

I have a 95 Metro with a 1.3 Auto trans. I purchased a JDM replacement trans. It looks like it came out of an 89 (has a K code on it). I have been told they are not interchangeable by a number of people. Now the company that sold it to me says the one I got is right and the K means nothing and if the one I got came out of an 89, the mount would be different. Is this correct, and can someone tell me how to tell the difference between the 89-94 & 95-up? I don’t want to try and put this in until I know for sure its right.
Thanks for your help