No you can not use a B-1 M/C Casting, We ordered the castings special from Brodix, they come with no seats, guide holes, spring pockets etc. They are basically a raised port B-1 Head. The valves are appox .600 to .700 longer than B-1 Heads. On the outside it looks the same and has the P part number on them still. They have other changes as well. Call if I can help you out.