Gene Deimling wrote
... you can buy the lettering for this car from CDS and
Greg Komar produces white lettering set for the 1937 AAR
car, and a yellow lettering set for the postwar AAR cars
with 10' inside height (series 4000-5298).
CDS produces a set with yellow lettering circa 1952, but
I don't know whether the data corresponds to the prewar,
or postwar, designs.