I've got a 360-2bbl Manifold and I think I've only got 1 Temp sensor screwed into it. Is that usually the only one on the manifold?

 

Temp sensors reside in the cavities that cooling passes through but that's not to say
that someone didn't tap a new hole for a sensor to control their electric fan. Vacuum
ports are drilled in the cavities ( or runners ) for fuel passages. If you have an extra
port in either and plan not to use it put a threaded plug in it. Depending on the year
of vehicle the manifold came off there could be various ports of both type especially
during the "emission's" years. The heads on my son's car were ported for air that
was supplied by the air pump on an 80's car to dilute the exhaust gases. A kit was
available to plug the ports for use on non-emission engines. You can usually plug
any ports not required for your engine.