I have been told by Borghi that all Morgan filler caps on recent models are 044. I ordered a spare cap from the manufacturer as I wanted to make it so that I could open it with the ignition key and it was 044 too.
This was after an incident where I embarrassingly left the fuel cap key at the B&B. Just managed to make it back, coasting down all the hills.
End result after a little careful locksmithing and I now have a fuel cap that is compatible with the ignition key. By shear luck it still opens with the 044 key too.