Looks to me that transmission is the original to the truck. Cast # 591615 is listed here at the top of the page:

http://chevy.oldcarmanualproject.com/parts/1929_54/260.htm

This may be a useful read: https://chev235guy.blogspot.com/search/label/Fixing%202nd%20and%203rd%20gear%20clash

Link from here: https://www.stovebolt.com/ubbthread...oper-sm318-syncro-rings.html#Post1182444

Last edited by Gord&Fran; 11/08/2022 3:22 PM.
Gord 🇨🇦
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1954 1/2 ton 235 4 speed