Bicounty - A little web searching located the following current resources related to rebuilding your 1950 3100 3 speed:

1 - GM CHEVROLET 3 SPEED S/M 318 REBUILD KIT 4 BOLT 1940-1954 ENCLOSED DRIVELINE - (further description indicates the kit may not include all necessary needle bearings and no mention of the synchros)

2 - BK131A - GM Chevy Muncie 318 3 Spd Transmission Rebuild Kit 1950-1969 - (this kit appears to include extra parts that won't be needed on your 3 speed as they apply to later models of the 3 speed)

3 - Chevy 3-speed Synchro Ring, 1949-1954 - (a previously unknown to me part that further description indicates you can rebuild your 2-3 Synchronizer drum using 2 of these to replace the worn out Synchros) *

* This is a Canadian Company which has a link at the top of the page regarding US pricing.
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~ Dan
1951 Chevy 3 window 3100
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