While all four studs have drilled shanks for cotter pins used with slotted hex nuts, access to the bottom two is restricted so 5/8" 7/16-20 hex nuts and shake proof lock washers were used for those two studs. The top two are easily accessible on a '34 and 5/8" slotted hex nuts and cotter pins were used originally. Michael Driskell (Third Gen Automotive) has both plain and slotted 5/8" 7/16-20 hex nuts in the correct S-2 (raven) finish.