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overheating at speeds indicates a water flow problem typically, because you have MORE than enough air flowing through the radiator at speed.

common problem is the old soft rubber of the hose
"sucking shut" and stopping flow through the system, which is why so many have springs inside of them. the wire coil is wrapped around to prevent the rubber from pinching closed under negative pressure.

if you don't have one laying around, an old coat hangar can be cut and molded into shape and slid inside the hose to serve the same purpose, and it's free



Good advise. Rev the engine and see if the hose is trying to suck closed. If there is no spring in there, you should put one in there. Like what was said, a piece of wire wrapped around a broomstick handle will work just fine.