I just called them about a 383 piston.On their website they list a 3.905 bore 4.00 stroke 6.2 rod.I posted on here about the rod length not being a ls1 standard length.So, the guy I talked to told me without running the longer rod,your #8 piston will smash into the reluctor wheel.I then told him most people use a 6.125 rod in a ls1.I then ask him about ordering a custom set to work with a 6.125 rod.$955.00 was the quote.After hearing that I then asked why Diamond and Mahle both offered a 383 piston using the 6.125 length rod.He did'nt have an answer.I really wanted to use JE,but I will go with diamonds...Will the diamonds be machined to clear the reluctor wheel?