Some trucks like mine have the engine oil cooler in the rad, it was also a stand alone cooler on some models in front of the radiator... I know the diesels got it for sure, but never paid attention to gas models.
Outside of the 6.5, I think the standalone oil cooler was on earlier trucks, but I don't have anything to back that up. Mine is in the radaitor, and while it probably does warm the oil in the winter, it's still going to dump excess heat, once up to temperature. It won't get rid of as much heat as an external cooler, but we probably don't need it, either. The oil cooler ports in the block (or adapter) aren't that big. If we needed bigger oil cooling systems we'd probably have it, like marine engines do. Reading BBC Gen VI threads on some of the marin forums, they don't use the GM ports, but rather oil filter adapters with much larger ports.
I've comteplated blocking the oil cooler ports, and removing the leaky lines. I'm dripping oil all over the place right now, and am already putting money into the front end.