How to drive four nixie tubes with arduino?(in-14/clock)
To create a Nixie clock you either go with the much older technology .... 74141 decoder and a latch, or modernize your circuit to use far fewer pins and readily available components. 

I'd suggest you could use the Microchip/Micrel 5822 8 bit shift register and high voltage driver which is more than capable of driving any Nixie tube.
 
You need 40 cathode drivers for four Nixie tubes so 5 * MIC5822 chips are needed.
Connected as a serial shift register you would need a single clock, data line and strobe from your MCU, and connect the data out to data in for the rest of the chips.
You could use the *OutputEnable signal to modulate the brightness but this requires another pin on your MCU.

Since the MIC5822 has an internal latch  you only need to update the shift register at the rate of your fastest digit change, 1 minute or the update rate when setting the time. This makes for very simple software with no fast update timers or interrupts, and only requiring 4 pins maximum on the MCU. 

The MCU data connection would look like those shown below ...note I have not shown VCC/Gnd or cathode connections:   







simulate this circuit &ndash; Schematic created using CircuitLab