[Mr70]

That's not unusual,especially with a bone stock 302 in front of a 3:73 @ 60mph.
Your car was intended to go quick off the line,not go for miles & miles non stop @ 60-70mph on the interstate for long periods of time,like the family station wagon.
Your reading head temp.not block temp.,so it's not as severe as you think.
Head temp.is always hotter then block and not a true internal overall reading.
Trying driving @ full speed with the heater blower motor fan on high,and see if that helps dissipate it to a lower temp.
Many other good suggestions have been listed that might help lower it.
I'm pushing a 4:10 behind my dead stock smog L-78 Chevelle,and found installing a 160° thermo & flushing the entire cooling system lowered it severely.