Well, it took me a while to go down that rabbit hole
, and unfortunately not alot to show as far as a modern replacement rear shock for your Panel.
Roaming through multiple paper GMC and Chevy Master Parts Books, plus electronic Parts Books resources as well, led me to at least some possibly useful facts. I found that the 1952 Chevy 3800 1 Tons (which should be the same as the corresponding GMC 250-22 1 Ton trucks) listed the rear brakes as an RPO (Regular Production Option) 200 under the complete RPO GM# 3707900.
The shocks for the Chevy RPO are listed as Model 967U / Valve Code 8J10/A1 and for 1950-53 the shocks were listed individually as GM# 5513639. As of 2-1-55, they were replaced by GM# 5303490, which are identified as Model 667U / Valve Code 8J10/A1 and again cover the years 1950-53. It gets even more confusing in later years as many changes continued through 1979, but the latest GM# 4940673 is listed for 1950-53 1 Tons and 1955-62 D-D 1 Ton (Dubl-Duti Panel Trucks) with a different Model code 684U.
After all that rabbit hole chasing, none of the numbers actually cross reference to a modern shock. :
As "Joe H" suggested above, you will likely have best results finding something to fit by comparing all your existing shock specs/details (including top and bottom mount styles/designs) with the Gabriel Guide he linked.
Best of luck in your search!
PS - Below are pictures of a 1953 GMC 250-22 Dealer pamphlet I recently acquired, just offered in case you and others would like to see it and perhaps use some of the info it contains as it very close to the same as your '52. NOTE: Rear shocks for the 250-22 are listed on the last page under "options".
