Kelsey Hayes SBP disc brake questions

The extra set I have in my garage for my '66 uses caliper to spindle bolts that are 1 1/2" long on the whole shank, a grade 8 castleated bolt head with a 5/8" wrench size. The threaded section of the shank is about 1/2" long and has that little plastic button in the threads to keep the bolt from vibrating out. Like I said before, the machined part of the shank is 7/8" long.