Look on the end of the trunion bearing caps. (the bearing between the rear tires that hold the rear suspension to the leaf springs.
My 1952 has a date on each axle and the trunion caps. Along with the data plates.
Does the truck have the 3 legged fording cable next to the glove box. All of the REO trucks up to a specific point in production, around late 1952 early 1953, had that. Mine does and is 107871. My 1953 truck doesn't and is number 119422. Hope this helps.