/6 overheating need help.

Have a photo to share? I gotta wonder if the electirc fan and all of it supports are reducing/blocking arirflow at higher speeds. Thsi would cause your issue as well as a poor flowing rad.

Have you lowered the coolant in the radiator top and looked to see if there is a lot of crud in the tops of the tubes? If a bunch of crud got loosened up, it could be blocking a number of the tubes, and that would be most evident with higher eingine loads (i.e., while driving, not idling).

Is the spring in place inside the lower hose to keep it from collapsing when the pump is sucking more coolant when the engine is revved up?