I thought I asked before but cound not get search result. Would the 74 125 piston/rings work on a 72/73 125. I know the 74 shares many parts. If not interchangeable using 73 piston and 74 rings could the 74 combo work in 73 at3? What could be the interchangeable issue or was that just a number change to the 74 444 prefix.

Contact Enduronut.   Ring designs and the corresponding piston ring grooves changed a few times.  You don't want to put a keystone ring into a standard groove for example.  

thanks Mark T!

You're welcome, and he might have the rings you need?  He told me a while back that he still has a decent stock of pistons and rings for these old bikes.  

I sent EN an email today.