Also I'm about 97% certain you can put an oil cooler on the 4.8/5.3 too!

This shows where it bolts to the back of the block with them two tubes. On my Z with the 5.3, all I have is a manifold that's bolted to that area and that's it. Same two bolts and all. So common sense would dictate to me that if I had the part shown in this pic I could then just get the plumbing between the radiator and the oil cooler manifold and have my oil cooler!