Around 2005 or 2006, GM started using a 58-tooth reluctor wheel, where before they used a 24-tooth wheel in the LSx based engines (LS1, LS2, LS3, etc.). This wheel is used as a way for the computer to detect where the crankshaft is at in its rotational cycle. I have done a lot of research, but have found no credible source to tell me exactly how to tell. I believe there was some overlap in model years where GM used both wheels. The reason this is important is the PCM is specific with respect to the wheel.
How do you tell which engine has which wheel without tearing the engine apart?