I have a friend that's building a 1970 900" ironhead chopper. he has been unable to locate a specific case bolt (old one no good) This bolt is the only "allen" bolt on the cases. It is the bolt that goes from top left of cases into top right case. It is not one of the three bolts on lower right case and is what looks to be a 5/16x24 or 5/16x18 bolt about 3 1/2"-4" long. He has been told by HD that it is no longer made. ? Thanks for any help you can provide.