Attention, everyone who has spent the big money for aluminum heads. DO NOT GRIND THEM just to fit the MSD distributor. Our mechanical distributor fits with plenty of clearance. It also will keep timing exact throughout your rpm range, which leads to zero retard, which leads to more topend. . Jim Guy is trying one out, and was blown away, so far, by the performance and fit of it. He is at MM in St Louis right now, testing it further. So far, he loves it..