If you look at bthe Standard Aircraft Characteristics for the F6F-5, it shoows under Fuel and Oil that the aircraft can carry 250 gallons in the fuselage, 150 gallons in a fuselage drop tank, and 300 gallons in drop tanks on the wing, I believe ALL F6F aircraft could do this ... but it also wasn't standard procedure. Perhaps thay were short of drop tanks or , more likely, the missions weren't so long as to require that fittment.
Also, because it COULD carry three 150-gal drop tanks didn't mean they HAD to be that size. All it means is the plumbing was there and the pylons / shackles could handle that weight, probably NOT under combat conditions.