I am pulling the head of my 1956 gmc 270 ci engine-it looks like the temp sensor in the head has two nuts- a larger hex one and a smaller square one. I assume (can't find it in manual) that removal consists of loosening the larger hex nut CCW. Anyone know how these go?

Well, my time went so quickly,
I went lickety-splitly
Out to my ol' 55.
As I pulled away slowly,
Feelin' so holy,
God knows, I was feelin' alive..... Tom Waits, Ol' 55