Tom,
This says 16 gallons in 1948; and, it also says that all 3100 1948 gas tanks were the same size (probably the same tank in regular cab and panel-body).
16 gallons here, too; and, my interpretation might be incorrect, but that 16 gallon between-the-frame tank was used in panel-body trucks through 1953. Regular in-the-CAB 49-53 tanks were 17.5 gallons.
