Hot running F-150

1991 f150 XLT Lariat Ext. Cab 4X4 Auto, Truck runs hot 210 to 225 deg. Engine rebuilt 4 yrs. Ago (302). So far it has a new radiator, fan clutch, water pump, hoses, 3 thermostats 195 deg, mechanical temp gauge. Two years back about.5 miles from home the lower radiator hose let go, I drove it home and temp gauge on dash reached the hot side. I parked it and the next day changed the upper and lower hoses, added new antifreeze. Started it up waited til it warmed up topped off radiator and recovery tank, put cap on. Took it for A ride temp gauge went over tward the hot side, to the L in normal and stayed there. For the last two years the above mentioned items were replaced one at a time with no avail. I installed the mechanical temp gauge to better see the temperature, thats how I got the temp numbers above. I checked it out with a inferred temp gun, the thermostat housing read between 205 and 210, various spots on the intake read about the same. Lower rad return hose red 120 deg. Inlet heater hose was 160 deg outlet hose 140 deg but I get very little heat in the winter? When the truck is started cold it warms up in the normal time range maybe between 5 & 10 minutes or so, thats idling not driving. You can watch the temp gauge climb up to 195 then you can see it drop off a few degrees when the stat opens, then from there it slowly climbs up to about 205-210 and stays around there. When you drive it it climbs right up to 220-225 then in a few minutes it drops back to 210 and then back up again, and it keeps repeating this cycle. It doesn't matter if you drive it hard or easy it still does this. One thing I find strange is that if I shut it down for maybe 2 or 3 minutes the temp gauge goes from 225 down to almost 180 deg like a rocket then climbs its way back up? Any help would be much appreciated. Thank You Mitch