Cabs are the same.
Fenders, hood, grill, and related parts are same for 1/2 ton, 3/4 ton, and 1 ton. Short running boards are same for these trucks too
Fenders, hood, grill, and related parts are same for 1.5 and 2 ton.

2 ton is a little wider front track width than the smaller trucks. I believe that 3/4 and 1 ton are same and wider than 1/2 ton by a tiny bit. Plenty of dimensions like these in the shop manuals and "restoration packs" GM once sent out for each year if you asked
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0202.htm
http://chevy.oldcarmanualproject.com/chevyresto/index.htm

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-