The tanks are 13"x18" with about a 3" radius on the long corners.
I calculated 55 gallons completely full. They have stickers but are painted over, I'll look more closely for tags but was surprised not to see them right off.

Grigg

•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-