misreading temp gauge

Question... Do you get a ping or spark knock under load ? Idle seem to climb and cause a diesel or run on at switch off ?
Questions are based on a my similar experience with or first Barracuda many moon ago.
Those gauges worked fine. Engine running a little too warm wasn't really a problem unless I got caught in slow moving traffic.
I wasted a lot of time and money on all of those less expensive possible cures.
A new radiator was the cure.