In 1948, the Chevrolet truck radio was expensive. Trucks were used for work so not many radios were purchased.
That's one reason why original truck radios today bring a 10X higher price.
Certain year Buick and Pontiac radios will fit in the Chevrolet truck dash (1947-53) opening quite nicely.
Back in the day a truck owner could wait a few years and eventually pick up a used car radio, in the wreck yard, a lot cheaper.
I think what you have is a "period or era" correct part for your truck. A part of history.
It is a Delco "Master" model 984170 used on 1946, 1947, 1948 Pontiacs
Not to be confused with the "Deluxe" model which had pushbuttons.
The original model number may be found underneath the radio cover.
I could not find another picture of the faceplate.
This will be an expensive radio to repair.