Light & Medium Duty models for GMCs were at least 1/2-1 ton, might have been through 2-ton (different from the Chevrolet truck size-terminology.
Light Duty: 1/2, 3/4, and 1 ton (100-250 series)
Medium Duty: 1.5 and 2 ton (300-350 and maybe 280 series)
Heavy Duty (GMC) over 2-ton
Light duty and medium duty cabs were the same - some windows, too.
I am still not sure about 54/55-1st SS "deluxe" door window trim being SS inside and out.
Maybe Greg Hill, or others, know? Much of my documentation has not been unpacked.
Simplex:
here's an old thread on this topic
