There have been no posts but I have been designing the replacement circuitry for this ancient box. The shift register PCB will be delivered soon. Originally I thought I would use an ESP8266 or ESP32 module to read data to display over WiFi. On further thought there isn't much you can send over the air to numeric nixies so it would be a waste of technology. Instead I will connect a STM8 based clock board using a DS3231 TCXO for accurate timekeeping, briefly described in #Quick and simple STM8 board with TCXO.

So there will be three small boards to put into the case, the clock board, the shift register board, and an off the shelf 12V to 170V boost converter. The whole thing can be powered by a 12V wall wart.

The picture above shows the clock board being tested with a TM1637 display.