I built my own breakout board for a set of IN-12A/B Nixie tubes. It uses a shift register and a pair of the Russian clone of the 74141 chip. This way, you provide only have to shift in a packed BCD byte to display your number. The boards can even be daisy chained. More information is on my personal website (see below).
Are your CAD files available anywhere? I am trying to find an accurate IN-12 footprint to use in KiCad.