Over heating problem

[Steven67c10]

Hey guys, so I just bought a 69 c10. Truck has a 350 with aluminum heads and cam. Truck has a/c as well. Well when cruising down the highway at about 65 it’s at 3200-3300 rpm. It starts to go up pretty quick. When I noticed it going to 220 I slowed down and pulled off the highway. I’ve noticed it only does it when I’m on the highway and staying at or above the 3k rpm range. At idle and just cruising around town it stays at 170-180 all the time.

Any help on what I need to do to fix this problem. It has dual fans but maybe I need a bigger radiator. Maybe a new thermostat sensor?

Thanks guys