I put Factory type Yankee 77's on my '64 C-30 back in '81. Although I tried to find some, they were no diagrams available back then to put them on in the correct position, that I could find anyway. I went to Junk Yards to measure some Big Bolts, only to find out there were more than one variation. The dealer or owner probably installed some of those. Anyway I went by measurements that I belived to be correct and was satisfied with the results. Today you can find those diagrams online. They have been posted a few times over at '67-'72 Chevy Trucks.
Bill
