It looks original and not much modified I say “mostly original” which covers all the little changes and perhaps 216 to 235 engine swaps done over the past 70 years just to keep the otherwise more or less original truck on the road.

•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-