check for actual water flow in the rad with the cap off and thermostat open.
Sometimes the water turbine in the pump is fubared, even on new pumps. Wouldn't be the first time.
Check for lack of advance at hiway cruise :
To see if you have a cruise timing issue, temperairly advance the timing so that it peaks out at 42-46deg at 2500rpm (your hiway cruising speed engine rpm) and go for a ride. To simulate if you had functioning vacuum advance.
Do not go WOT with the timing set like this.
if the temp guage settles down with the extra advance, there's yer sign.
reset your timing again, before WOT use.