There is something funny with that circuit. Some connections are apparently not shown. The zener is there to suppress spikes, as noted earlier.
1) Both devices must have a common ground. Thus, the circle above the input needs to be ground too.
2) There is no supply to the output. That is, where does the 5V come from? A pull-up resistor will do that, which isn't shown, but may be part of the new cluster. The output will be inverted compared to the input, but that may not make a difference, particularly if it is reading frequency rather than pulse width, which I assume.
3) That is a large capacitor (relatively speaking) from gate to source. The on/off transitions of the mosfet will be quite slow. That also may not make a difference, depending on how the new cluster works and the frequency of the signal. In other words, the RC time constant is roughly 1 mS, which may be insignificant if the max signal frequency is 100 Hz, but if it is >1 KHz, then it will make a difference. It probably needs a turn-off resistor, unless the signal source is low resistance. If it is very high resistance (probably unlikely), the gate could stay turned on a long time.
In other words, given the noisy automotive electrical environment, that design might well work, with the caveats mentioned.
John