If you guys are still looking, I ordered a kingpin set off of Rockauto for my 54 3800. It was a few years ago and I was able to get an AC Delco kit, I might have the part number still. They still offer one with a .921 pin that's being sold by Moog.
1954 Chevy 3800 Long Bed: ex-fire truck turned farmer's town run about turned 353T powered retirement project 1953 Chevy 6400: the work truck