If you also get the brackets it could/should work.
Keep in mind that there are different sizes of frame mounted tanks, you may only be able to fit the smallest that were mounted inside the frame, used for the pickups. Most anything other than a pickup had the tank mounted outside the frame and I think were longer.

This might help a little.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0802.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-