[Arran]

I'm not certain about what you are asking, if you are asking whether you can convert this single ended amplifier and power supply into a stereo amp then the answer is maybe. The question is whether there was anything else attached to this unit, if it had a tuner chassis plugged into, and powered off of it then you might be able to use that transformer to power a duplicate amplifier for the other stereo channel. However if this was just a single ended amp from a phonograph unit then it's really just a guess as to whether the power supply would be enough. Where was the EZ80 tube located, I see two tubes in two sockets, and a third in the end with nothing in it? Where are the controls, like the power switch, volume control, etc? Do you have a schematic for this unit?
Regards
Arran