Over heating on the freeway?

Cope said
71 dart, new 360
New griffen cross flow radiator. Restrictor plate in T stat housing.
Large eletric puller fan and shroud.
All new hoses.

The car is fine around town, 180-190 but get on the freeway and the temp just cimbs...

This is so backwards from all other cars I've ever owned I'm not sure what gives?

Any ideas?
Click to expand...
Shouldn't even need a fan at freeway speeds.
The under carriage opening around the engine will let the air escape, so forget the hood scoop idea.
The fan, if on, could be blocking "not keeping up" ..the other issue is usually a capacity one...or you have too much timing and it's just pinging...or even too retarded.