1947 Truck Specifications Manual - Page 93 - fuel tank was clamped to the outer side of the right-side frame member - on all 1947 trucks.
Filler location on right side - for all USA trucks.

1948 Truck Specifications Manual - Page 93 - fuel tank inside of frame for small trucks (3100-3800) and outside of right frame member on large trucks.
Filler location on right side - for all USA trucks.