what is the lower sensor that goes into the radiator
 

I have a chevy racing radiator in my TII project.

I am going to have it modified with a different neck on the bottom, but Im also going to have a fitting for the level sender.

but what is the other sensor on the bottom???

I dont want to have it added if I dont have too.

iirc, it connects to the oil pan - I think it measures oil temp, but I'm certain I'll be corrected if I'm wrong ;)