I checked gm part wiki and found you likely need part number 379656 (see attached image) It is a 27/32-20 thread 1946 to 1958 all 3/4 and 1 ton use the same nut
And it looks like O’Reilly auto parts has them for $10 in California But nothing beats original I bet you could find it for nothing in a local junk yard -s
