Man I like your "pickup". Very cool.
According to the 48-51 Truck Shop Manual the 2 ton models had larger (1.109") king pins than 3/4-, 1- and 1 1/2-ton conventional models which did share the same .921 diameter.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0316.htm
Good luck!


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