JW51,
Lets see if I can help out.

Attached are pictures with basic measurements of a +10 oversize NOS bearing from a kit I have on hand. Kit was just one of many spare parts (boxes and boxes) that came with my '51 3100 when I got my Grandfathers' truck many years ago.
I did search for a modern number using the original GM# 373476, but could only find a scattered cross reference listing of about 5 manufacturers (and10 different part numbers). None of those show as available through any of the original manufacturers though. Did find an active number that kept popping up in searches through Napa (262-1296) but the on-line listing says "Not Vehicle Specific". Maybe possible to take my part to local Napa and see if they match???
Also noted that your location says Missouri. I am in the SE corner of KC metro area. Give me a shout if interested in meeting up to help wrangle this part need.
Worst case scenario, you can get a complete new king pin kit from one the many vendors that carry them.
Let us know if helpful.
Dan
