Stepped Head Bolt Bushings/Washers 1/2 to 7/16
I've done it both ways, with and without the bushings. I feel safer with them installed, however. ARP makes them, actually they make them for Edelbrock (or used to anyway), but they're about the same price from both places. I ended up using an ARP head bolt kit which came with the bushings. I think it was around $105 or thereabouts.