5skj3888

5=Kansas City plant

SK= 1949 4400

J= October assembly

3888= 2888th truck off the KC line that year.

source: oldgmctrucks.com

I'm looking at the reprint manual you reference and I agree that it doesn't show the 2speed rear for that truck. In fact the truck rated at 11,000GVW didn't have the overload springs. Could be someone added the whole works from another truck sometime in it's lifetime.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.