Hy Grigg, the 57 Chev 8100 with Eaton axle [485?] uses a kingpin which is 1.109" X 7.5". I had a heck of a time finding these 15 years ago, seems to be an omission in most parts books, mine needed to have two lock pin grooves, could only find one groove type. Sealed Power p/n 808-389 kit with shim type thrust bearing, may be the same as TRW K389, Sealed power p/n 808-439 kit with ball type thrust bearings. The part number for the pin alone is 2251845 = Eaton 32310, hope that helps.