its funny how we are obsessed with bolt head markings, my original bolts for the spring covers had no markings, when i was removing them several were rusted bad and i had to drill one out. since a couple were missing, i just bought the amk kit and used it. I tried using all the original parts i could in the rebuild, but found it was cleaner using amk stuff. just felt like i had to throw that out there.Dearborn 10-20-1969