Sleeves insure good thick cylinders and all even--Mega Blocks are good when they are good but some keep you from boring bigger --Mains are way stronger in the KB, Indy style blocks vs. Mega blocks--the cross bolts there are not that big a deal--I have seen plenty of cap walk on Mega blocks--You can fix an aluminum block but busted iron is usually candidate for coffee table art My take is a 572 on the street is like driving the Zamboni at the ice rink