I just had my engine rebuilt. My builder pretty much said any street legal oil will not have enough ZDDP (zinc, phosphorus) in it. You will be looking at an off road/racing oil to find the correct amount of ZDDP in the oil. I believe you want 1200-1400 ppm. There is an older API rating that would work but cant think of the rating. I personally chose Brad Penns 15w40.