Does your car run hotter at higher speeds?

I've been driving my 68 dart for about 8k miles. So far on the freeway at around 70ish, or higher, it stays hot. Once you back off to 60, it cools down, and idle cools it down further. Switching the heater on allows you to drive slightly less hot. I have literally replaced every cooling piece on the car - except the radiator. I even took the head off and cleared the water pathways and still heats up. I flushed the radiator and the car doesn't heat up as much. The water pump replacement made the car heat up faster and I believe the car has a 180ish thermostat on it. New pump, hoses, head gasket, cleaned the ports, new fan, etc... So I bought a radiator, and I'm putting it in tomorrow. The only other thing I could think of is the oil pump not pushing well, or the oil filter clogged. Not sure, but oil filter is brand new.

I've had the same issue for a while as you have, and tomorrow when I swap in the rad, I'll let you know if that fixed it. Likely you have the same thing and the rad is just clogged. I've been dealing with the high speed issue for a while, but can only stay on the freeway for about 20 minutes, so if you're in a lengthy drive, either your rad is clogged less, or something completely different.