I bought my avalanche new off the lot and I now have 800 miles short of 300,000 miles on it. My oil pump failed so I am going to go through it and freshen the engine up. Here is my conundrum by the vin cod I have a flex fuel ( vin code z) that is confirmed by my fuel rails being stainless. So by that I should have a l59 engine. I have removed the engine but by the manufacturer code on the block it cross references to the lm7 block (vin code t). Has anyone else had this issue.