Just a heads up....this guys is selling replacement (needle cage) bearings for the Chev main shaft on Ebay:
http://www.ebay.nl/itm/172104151100?...%3AMEBIDX%3AIT
Ebay object number: 172104151100
I bought one about a week ago and have fitted it to the gearbox in the meantime; will post a picture in the next few days.
Different manufacturers often use the same part number for the same bearing, so it helps googling just the part number
without the original manufacturer and adding the word "bearing" or "seal"....and see what comes up. Sometimes this results in replacement bearings available through agricultural suppliers...or ads on Ebay. It's also how I found the ad above.
Google searching will often also give you sites with cross reference lists.
Alex