Thanks for the info, Gruder. I'm not in it for the bling, so unless actual testing shows different results than your calculations, I'll stick with the stock head. There is a fair amount of weight difference in the alloy vs. stock diff cups also, even though we are talking grams. I wonder if the extra strength they provide is needed. I'll have to get more than 2 months on my car to be sure, see how my diffs hold up. Although I haven't had my car long, I have alot of hours on it, 10-12 a week. I go out nearly every day for an hour or more, 3-4 on weekends. The only problem thus far is to be expected with sand, bearings wear quickly. It is tons of fun though. Keep us posted on your progress, Gruder.