360 running hot

OOPs, the teener A/C rad is supposed to be a 26. Or at least Mine was/is a 26.
But your combo should be fine with a 22.

Dropping the initial to 12* with no other changes is the wrong thing to do. That engine wants more cruise timing; a lot more. Pulling 4* out will just make it worse.

Keep your eye on the gas-gauge when the temp gauge goes up. Those two run off the dash-gauge regulator. If the regulator sticks, it will send both needles to the top.