You should use the 160 and pay no attention to anyone who does not live where it is as hot as it is here in summer with no offence to our brother in PA. I do not have a thermostat in my 66 Mustang at all and it never overheats, even on 100 plus days because I have a lot of coolant flow. Use the 160, the car will still warm up and run fine and you will have heat in winter, assuming you have a heater
. The water will stay at 160 until you overtake the efficientcy of your rad like when it is really hot or you are on the track or something. As long as the rad can exchange the heat, you will stay at a blissful 160.
It just won't be barfing its guts out on hot days...
Your overflow tank is empty when the engine is cold, right? You only have a bit in the bottom so there will be no air?