What makes you think the oil temp and engine temp are so different? if you are worried about the oil exceeding its rated operating temperature, i would ask what you intend to do about it if its too high? slow down? i personally would not do it, Maserati clearly don't think its needed.
I think it would look a bit daft in the air vent hole. I would mount it to the drivers side of the instrument binnacle between the instrument binnacle and the windscreen pillar, its a spot where there is a natural space. Or see if you can get an electronic meter that's flat and mount it to the left of the steering column on the surface of the dash. mostly i wouldn't do it! Another thought might be to get a blue tooth sensor and app for an i-phone and mount the i-phone on the dash some where, this would allow you to do many things as well as monitor oil temperature, i have dash command on my i-phone and with a wifi ODBII plug in i can pull up all sorts of dials and engine management displays real time and log them, its quite a good tool. unfortunately to integrate a new oil temp sensor into dash command it would need to be on the CAN bus of the car and that's not an easy thing to do i don't think. good luck with it whatever you do.
