These are just some pictures from my B7971 clock project.
The enclosure is a piece of extruded aluminum. Some angle pieces make the end plates.
The colon neons are supported on thin steel (hypodermic) tubing with clear heat shrink.
The CPU, nixie drivers, and power supply boards are all modular. They just stack end to end.
A rotary encoder sets the time/date and other features. A sensor auto-dims the display in low light .
Pretty simple electronics:
Supertec HV5522 HV drivers for the nixies
Sorry, no schematics or plans exist (this was a one off). If enough people are interested, I could draw up the schematics and post the code.