1985 mustang temp problem maybe?//?

well let me first say that i have a 1985 ford mustang convertable lx. It has a 5.0 L engine with a CFI unit and i have replaced the radiator with a new one, it has 3 coils, about a year ago, along with a water pump. And i recently replaced the thermostat and the overflow tank because i live in arizona and its always had an overflow problem, well all i had to do was replace the thermostate and whalla! all problems solved but i still had a little rust so i flushed it and thats where my new problem started. I used a standard flush and then my temp guage said max H! with key in accesory and a cold engine, so i figured a new temp switch would fix that but it only sort of fixed it?. . .

After driving for a while. . like 30 min.. . well warm enough it says its too cold its after the large C but below the normal bracket . . if ur familiar with the older guages. well i took the temperature with a thermometer after i turned off the engine and it read 160F i know my thermostat is 180 and i know 260 is high but is 160 too low? or do i have a problem and if its normal.. what do u recamend i do with my guage read problem?

"and its always had an overflow problem"


Might wanna check the cooling system first. i.e. head gasket, thermostat, water pump, ECT, etc.