It will probably run on OS4 on a classic. That said, I'm sure there was an AHI version of the narrator.device on aminet some years ago.
I once tried to get the AHI version to work, but it wasn´t working out of the box - I can't remember the details now.
The easier way was to use Flite from Os4depot. I even wrote a GUI-Program for it that would read the clipboard. But I never updated it to work with the new version of Flite and my GUI crashed if your clipboard contained more than 4K of text.