1972 C10 400 Engine Sensor Help

[lintcollector]

It is spring now so my daughter and I are back to work on trying to revive her 72 C10. We are rewiring with the help of Painless Wiring harness, but are now stumped and need some help.

I am not cool enough to embed the pics in order yet, but here's what I'd like to know:

1. Image 9816 (wiring diagram) -- Is this item what I am pointing to in image 9817, and what is it called?
(I am thinking it's the switch to tell the thermostat to release the coolant though)

2. I have gone through the wires I removed from the truck, and I don't have anything that looks like it would/should be able to connect to item in shown in 9817. Can someone please provide/post a few pics of what this should look like?

Thank you in advance.