Great, that helps give us a much better idea what you're working with. Can you also confirm the distance between the two screw holes, center-to-center? Judging by the style, I suspect it may be something like 3-15/16", but I would like you to confirm.
If it is, c heck out our 82-069
and see if you could use this as a replacement lock. As for the mortise lock, I would need to know the distance between the screw hole centers there, as well.