And it works!
In a strange reversal of fortune with this build the 74165 circuit worked first crack.
I built it on the breadboard and the idea of using the machine pin socket for the 4021 as a jumper point worked a treat. It interferes with the arduino rails but the TFT lcd is easy enough to jumper to. I may decide to solder it into the spare footprint so I can mount the ethernet shield and try it. For the moment though, I’m a bit sick of it. I’ll put it away and focus on the 3mhz membership card for the moment.