So after listening to much advice from you and my mechanic I purchased a 5.3 long block from the dealer. Came with a 3 yr/100,000 warranty. My mechanic (20 yr friend) removed and examined parts from my AFM failed 5.3 before deciding if they were fit to go on the new engine. He got the engine in yesterday and was hooking everything up. When he removed the plastic cap from the oil pan to insert the oil level sensor module this is what he found! Still cast and not drilled or tapped! Pooched for the weekend as have to wait till. Monday morning to speak with GM. Don't want to void the warranty.