Josh,
The late 1954 Truck Data Book does not show chromed exterior mirror arms (or chromed/stainless mirror backs) in any of the RPO mirrors or accessory mirrors.
That Data Book does not mention if the standard interior rear view mirror back (and attachment arm/bracket) is painted, chromed, or stainless. My guess is that the interior rear view mirror arm/bracket was painted and the interior rear view mirror back was stainless.
Tim
