I think upgrading the oil cooler is a wasted mod for most people, if you track race the car then yes I definitely would go for it, but for street/strip cars I dont think it's really that necessary. I think you're better off upgrading the engine coolant system with say the Evans pump, thermostat and a much bigger radiator like the LFP which will in turn help cool the oil.
I regret putting more cooling in my Cobra about as much as installing the Whipple.