Why do you want to use the old mechanical instrument for water temperature (0-120°Celsius, for oil you need 0-150°C) ?!
You can convert all 12 Volt instruments to chrome/white needle-gauges like I did for my gauges holder on the picture underneath !
reading this answer I think I ought to explain myself a little bit:
I do not trust on the car´s dashboard gauge, because i have an electrical problem that makes me nervous about the accuracy of the meassured temperature value, the question is as follows:
when I start my journey in the car, it starts warming up well, and the gauge in the dash will show an increasing temp value, that is ok, but if you stay there without moving the car, the needle will go up until 2 o´clock, I checked the temp in the engine surfaces with a laser gun and it will be between 72 to 89ºC, so the car is OK, but the needle NOT
this has been driving me mad for months, but suddenly an unexpected thing happened:
I had a high beam problem, due to some electric problem like a bad earth, when I make the horn sound suddenly the high beam lights went on !
after some cleaning and renewing of front cables, and cleaning earth points in the steel, the problem was solved, high beam lights are now ok
so one day, I don´t know why, i push the horn while the car was moving and the temp needle was at 2 o´clock, and....the needle came back to 4 o´clock showing the real temperature and it maintained there for the rest of the trip
now when I started the car the last step before departing is to push the horn !!
I know it should be some kind of electrical problem still underneath, but now I can not check it properly, (I WOULD APPRECIATE IF ANYONE REALISES A CONNECTION BETWEEN HORN AND TEMP GAUGE AND TELLS ME WHERE TO LOOK) (i even have added a new direct earth to the temp clock in the dash with no improvement)
to make a long history short, now I do not trust in the temp gauge, and as I consider that topic a critical item to check if everything goes ok, I would like to install a set of sensors and gauges, so your proposal andy sounds pretty well, I am considering to intall an additonal gauge set of:
- coolant temperature (as a crosscheck)
- oil pressure
- oil temperature
- volts
now maybe you can understand what is beneath all this fuss
the motometer was a present from a friend, and I love the aestetics together with the fact of its accuracy, but if it is broken maybe I will move to fully electric complete set of VDO or... ANY ADVISE ON THE BEST MAKE, AND WHERE TO FIND THEM??
regards