I won't claim to say this is the best location to hook up a vacuum gauge but definitely gives a proper reading at idle assuming the EGR being disconnected causing a problem. The other way is to have a T connector so you can keep the EGR line hooked up. The fitting is at the front of the TBI right next to the large PCV line.
Up here they suggest a 195 thermostat but a slightly cooler one might be better for your location but with whatever you decide on, T stats don't cost a lot and I'd say its easier to just put in another one while your doing through the motions of draining coolant out anyway.
You had a new fan clutch mounted up for your drive in this morning ?