Hi Bob
Now I think I see where your question is coming from, two of the major sources of Chevy Parts like transmission parts have gone away, my old source for all this kind of stuff has been sold (Obsolete Chevrolet, Nashville, GA) and the company that I thought had bought them which I believe also bought MACs did not retain the old part numbers.
I have found all of the bearing numbers in the 1938-1951 Canadian Chevrolet Mapleleaf Trucksand it can post the part numbers but the are the chevy proprietary numbers not the New Departure, Hyatt numbers.
Then spent a hour for the fun of it trying to find any of those parts at the different Chevy parts sources. No luck.
Really glad that three years ago when I broke a 3rd gear tooth, found a NOS complete transmission and then found a new 3rd gear and rebuilt the other transmission and put it on the shelf. Now I've got a spare if any of my trucks has a problem because finding parts has gotten a lot harder in just a couple of years.
As has been suggested by Hanno if you have old bearing you can work through the dimensions.
In the past I have found companies like
https://www.motionindustries.com/pro...alogSearch.jsp had easy to use cross reference systems which I have not been able to find on their site right now.
Here are some numbers to start with though
Lower shaft front Hyatt C-1206, rear Hyatt C-1207
Pilot Bearing L&S 93424
Main Shaft rear New Departure 3307
Cheers Phil