There used to be a 3rd party producing PLC5 programming software. They were called ICOM, but AB bought them and changed their name to Rockwell Software.
Taylor Industrial Software may have produced a package for the PLC5 - not sure.
Teledenken is another possibility.
When I first learned Allen Bradley PLC 5's we used a software called TopDoc. It was DOS based, very clunky, and not real user friendly. I am not sure if it even exists anymore as we migrated over to Allen Bradley software. Guess you can see if it is still around.