And the clock is done.

I'm reasonably happy with how this has turned out, however I really wish breadboards' power rails had holes _all_ the way along the rails, instead of groups of five holes at a time. I had to place two wires and one resistor at a slight angle because of the five hole layout, but I wanted to compress the layout slightly and the final result didn't turn out too bad.

Next task is redoing the registers...