I've ordered some wires to connect to the nixies. They haven't arrived yet. I did some final prepwork.

I put some screws on the nixie PCB and glued it to the existing main board using a two component adhesive.

The other thing I did is replaced the resistor on the tube anode on the six nixie PCBs with a wire bridge. I also cut the traces from the kathodes so the tubes are no longer connected to components that are remaining on the main PCB.