Call Southward 541-431-0556 and make sure you use the same head gaskets and fasteners lengths on the torque plates as your going to use on your motor, they may not have the .022 thick small bore steel shims head gaskets for the 383 and 426W 4.250 bore size If they don't I do, they stop here regulary so I can loan them to them when they stop in here the next time