Can someone educate me on online 6 coolant temp sensors

[straight6chevyguy]

Hello everyone, so I'm working on my 76 C10 the truck originally had the integreal manifold head 250 inline six I have swapped in a new rebuilt block and rebuilt Non integreal head.
First off, it has been a few years since I took the original engine out of the truck so my memory is fuzzy on a few things.
Ok so, I'm hooking up my engine bay wires and I noticed that I have two wires that can plug into the temp sensor. Opon inspection I determine that the two wires are connected together. Ok so I know there is a temp sensor that screws into the thermostat housing.
Looking at my old head there is a hole that looks like a temp sensor could go this where my memory is fuzzy as I stripped the old head of all it's usable parts. I'm not finding another temp sensor anything similar In my parts don't know if I misplaced it or what but what I'm getting at is I don't know what was in that hole in the old head or what that second temp sensor wire went to.

I know that the older engines either had one temp sensor either in the thermostat housing or in the head.
So my first question is did 1976 trucks have two temp sensors? Or is it for something else?
And that leads to my main question. If there was originally two sensors will I need two sensors for my idiot light to work correctly?

Also, my new head has the hole for a temp sensor, my original plan was to run the sensor for the idiot light in the thermostat housing and a sensor in the head for an aftermarket mechanical gage, any thoughts on if this would or wouldn't work?