Temperature switch for 350 SBC with modern heads

[dmjlambert]

Hi
If this has been discussed before, I was unable to find a thread about it, so please bear with me or point me in the right direction if you can.

I have a gauge cluster and we recently discussed in another thread about getting the right sensor going for the stock instrument cluster gauge, and put it in a 3/8 NPT hole in the updated heads of the 350 SBC. Now, let's talk about the passenger side head and its 3/8 NPT hole. I would like to put an overheat temperature switch in that hole and wire it to an idiot light as described in this other thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=490161

So, what is the deal with temperature switches? I know they are sold in a bunch of different temperature ranges, and they come on at a certain high temperature and go off at a slightly lower temperature, and they are used for either overhead warning or to switch an electric fan on/off as needed.

What I can't seem to find anywhere is what is the temperature range of the stock 350 SBC overheat switch, which is a 1/2 NPT size, because I would like to find an appropriate 3/8 NPT switch with the same temperature range.

If I want to run an electric fan, what is the temperature range of its switch? I assume that is a different range since you want it to switch on and off at lower temperatures than a warning light would be switched on.

When I'm all done with this truck I might just have 3 temperature senders, one for the gauge, one for the idiot light, and one for an electric fan. At least a couple of them will be 3/8 NPT size and installed in the heads.