Model Train N/OO gauge Auto Reverse Stop Start Shuttle unit

I found two of these units in the garage which I built with my children when they were young and surprised to find that they still work. These are old design using 555 timer and a relay to reverse the power polarity. I decided to experiement using ics to replace the relay and after serching the internet for suitable components, I managed to build one, three rather. I have tested them on N and OO gauge but not yet on Z gauge.