Andrea, the oil temperature gauge is only for right preservation of the engine. It should be hidden in some kind of area where I will pout other instruments I just use for classic rallyes. I even think about an air fuel ratio gauge.
The main aspect is there a solution which I can buy to place the temperature sensor into the oil flow like the drain plug with an integrated sensor. Heard about an adapter for the oil filter which provides the possibility to mount an oil temperature sensor.