Chet is right. No metal to metal, so the fabric disks allow the shafts to flex. Also, don't use any lock washers. They will not work for this application, as the disks will compress over time and the lockwashers will loosen up. Better to get a machine shop to drill the holes for you and use cotter pins. Most castle nuts you buy will be grade 2, which is really not good. If it were mine, I would have some grade 5 nuts made into castle nuts, and also use grade 5 bolts. These bolts and nuts were not graded back then, but they used very good ones, somewhere between modern grade 5 & 8. As for the buckle washers, just replace the missing ones with similar sized large washers. I did that for a long time with no problem, until I found some spares off an old parts car. If you really want more buckle washers, I can look around, I may have a few spares left, but not many.