LT1S10..... factory oil coolers were in C5 Corvettes, Vipers, some Cadillacs, and I think, some early Boss Mustangs. The Chevy one had an adapter that fit above the oil filter.

I agree that gettng the oil temp up high enough is usually the challenge. We had an oil cooler on the rock crawler and took it off. The oil temp stays roughly in line with the water temp (180F) even when idling on a Tucson summer day.

Oil coolers on non-drag race cars are there for a purpose. Like a NASCAR car, the water cooling is marginal so the oil cooler supplements the radiator cooling. If your street car is that close to the edge, something is wrong OR you have a bazillion horsepower motor.