I don't know if this might help, but it's very hard to find any information on transmissions on line. This link is the best I've found on transmissions,

http://www.teufert.net/trans/trannyid.pdf.

Down near the bottom are the chevy trannys. Just looking at your pictures I think the side cover is from the 343 Saginaw because of the hump for the top bolt. Good luck figuring this out.

Tim


I am currently digging back in to a 1953 3800 (one ton) with a nine foot bed. I've owned it since 1979, and drove it until 1982 (or so). My wife got me involved in restoring it back in 2002, got the body removed and the frame redone, then things came up. Now I am retired and starting again. If anyone is interested I have photos on Imagur ( https://timwhiteblues.imgur.com/ ). I live way back in the woods in the Ozarks on 40 acres at the end of a 2 1/2 mile private road.

Tim