1968 Barracuda Power Steering Pump

Hello out there! I have a 68 Barracuda small block with a power steering pump that needs to be replaced. I am having a hard time finding a rebuilt pump. I fine plenty of listings for 1969-1972 pumps but not for the 1968. Does anyone know what is the difference if any between 1968 and later pumps? Or would it be possible to use a pump from a different year model? Thanks to all for the help.