It looks like both kingpin bolts were made out of existing hex head bolts. The top kingpin has a 15/16″ hex and is drilled for safety wire. None was installed. The shoulder is only a few thousandths longer than the bushing. I found this can create the problem of the bolts backing out during use. I thought the top bolt was drilled and tapped for a grease fitting. Turns out it was only center drilled. The bottom bolt has a 7/8″ hex and the shoulder is about 1/32″ longer than the bushing. The threads come up about 1/4″ short of the shoulder so the kingpin jams on the 1/2-20 UNF threads instead of locking up on the shoulder of the bolt. The threads are about 1/4″ longer than the top bolts threads.

I put SAE 841 sintered bushings on for the picture. I also have Delrin and SAE 660 bushings in stock.

The top bolt is on the left, the bottom is in the middle and one of my oversize thread bolts is on the left. I am going to have to use an oversize bolt in the bottom because the fishmouth is cross threaded at least twice, maybe 3 times. Ughhhh