temp sending unit and switch locations?

[GMC3]

I finally figured out that I need both. One is connected to the gauge and the other to the idiot light. My problem is that I have vortec heads and the outlets on the heads are different sizes than the threads on the switch and sending unit. I have an edelbrock performer vortec manifold and the rad hose runs directly over the outlet where one of the switches could go. I have 2 threaded openings in the manifold on either side of the carb that are the right size however I took the plugs out and didn't see any antifreeze in there. My question is will the sending unit and switch work properly if installed in these locations or do I have to find some alternative to thread into the head?

[neonlarry]

What year truck are you talking about?
On pre 73 trucks the temp sender in the P\S head is for the TCS circuit which can be disconnected.

[GMC3]

sorry. 1970 c10 2wd 350 w/ vortec heads, performer rpm vortec intake and the temp switch and temp sending unit I have are stock 1970.

[Longhorn Man]

the one on the passenger head is not for the light, as lary said, it was for a transmission controlled spark advance... a very primitive and crappy smog device that has been disabled and disposed of on 95% of the trucks out there.
Now, for the actual temp guage one on the drivers side... I *think* someone came up with a volvo unit years ago that fit the hole, and had the right resistance needed to operate the guage properly.