Here's an update. I pulled the thermostat and replaced it with a 160. Before installing, I drilled two 1/8" holes in the flat area and then filled with coolant through the thermostat opening as Dave recommended. On startup, I immediately noticed the top hose and the top of the radiator warming up. I confirmed circulation inside the radiator and then let it run for about 10 minutes or a little more. The bottom radiator hose was warm as water went back into the engine and hot coming out the top. The temp gauge went to about 140 or so, but seemed to hover in that area and no water coming out the overflow. So it appears, at least, that the problem was resolved with the new thermostat and drilling the holes. Probably had air in there somewhere to boot. I didn't run it longer, but don't think I'll need to at this point because the coolant circulation appears to be doing what it is supposed to do. Thanks one and all for the posts and helping me through this.
