Lloyd, your stud is a little too long. IMO. I can only measure mine from the flange up, but it is 1.500 from the top of the flange to the top of the stud. Mine appears to have a smaller unthreaded shank area above the flange. Original cowl hood wingnuts are plain steel and have small thumb wings, BTW. I have also included the correct short stud and chrome wing nut for non cowl hood cars, as well as the current repo AMK chrome wingnut compared to a known GM original which appears flash plated much like GM chrome valve covers.. Notice the thumb wings on the AMK wingnut are much bigger and extend to the inside more. I have heard that 67 427/435HP Corvette studs are the same, but I just measured 2 known originals, 1 a 6,000 Mile survivour and they are both 1.422 and 1.415 from top of flange to top of stud.
As far as I know mine is original, I have owned this RSZ28 since 1973.