Yeah, i`ve read it.

at cold outsidetemperatures it is 95-98 Grad
at hot outsidetemperatures it is 100-105 Grad

It reaches these temperatures while stand still. But not cruice! I`ve allso experienced the same as you. I changed the thermostat, because the temp rated below the 75 degree mark. With the new thermostat it resched a little bit above the 75 mark on the gauge. I`ve never tested how accurate the temp. indicating system is. But every V8 I get to see "in action" I find this "problem". I`ve imported a spare part car with a 4,2 (ABH) engine. And guess what - same on that one.
Come to think of it`, I`m not very impressed with the capasity of the cooling system. No other car I`ve had, or heard of, fluctuates from 70 to 100 degrees coolant temp. between cruise and stand still under normal system operations.