Both or none
Personally I'd shim the Oil pump and convert to a full flow cooler with a T Stat, pressure based just isn't the way to go as the cooler is active at all the wrong times.. i.e. When the Oil is cold/thick and the cooler isn't needed it'll be wide open, then when the oil is hot/thin and pressure drops the cooler closes just as it's needed...
Had to deal with that pileOjunk back in the 80's when I built the 240z/Toyota V8 combo and have been upgrading to a full flow system ever since.