The GM drawing for the part number shown in the AIM for the 1961 single WCFB carb stud has a shoulder. The function of the shoulder is to stop the air cleaner lid from being pulled down too low thereby potentially shutting off air into the carb. However, the 1961 Judging Guide is not clear on whether the original stud for the single WCFB should have a shoulder or be like the stud shown in the AIM for the 2 WCFB set up which according to its drawing does not have a shoulder. My question is, which is correct for the single WCFB carb, no shoulder or shoulder? If someone has an original 1961 that has the original carb stud please tell me whether it has a shoulder or not. Mike Bailey