Cant cool my 5.9 magnum. Radiator size or add one thing else?

My 367 is only a bit over 400hp, but I would not be afraid to tow a trailer to Texas.
Most dyno engine oils begin to smoke at 240ish. I'm guessing a little under that would then be the upper limit of hot.Unless of course you have mechanical issues like; the the valve stems start sticking,or pistons getting stuck,etc.But that's why I run a 7qt pan; it puts the cooling oil where it needs to be. Also why I run dual 3"exhaust, so the heat can get away. Also why the lowspeed circuit is a little fat; it sucks some heat out of the chamber.
The rad isn't the only way to get rid of heat.