1959 Buick 364 ci temperature sending unit location

I cannot seem to find the location of the temp gauge sensor on the engine for my 1959 Buick with a 364 cubic inch. There appears to be a sensor that is brass colored right on top of the manifold, in front just below the air cleaner, and just behind the thermostat housing, but it is on the manifold so I am guessing that is not it, and likely something else. I could be wrong as I am not a mechanic, and only perform minor repairs. Thanks for any help with this or pictures that can be posted of the location.