The Chev LT5 uses a thermostaticaly controled oil cooling system which works very well. During development, they discovered they had to use a progressive opening thermostat so it slowly bleed the cool oil from the cooler and lines into the engine until this oil was warmed up close to the oil in the engine.
Before they tried this, the engines used to shudder terribly on the test bed as the thermostat opened and let a big blast of cold oil into the engine. Doesn't sound like it would do the engine any favours dumping cold oil into the block when already at running temp.
I'm pretty sure the more common sandwich adaptors used to fit oil coolers just let the oil in the cooler and lines heat up as the oil in the engine warms up.
Good luck with it.