beltfed,
The 1948 tank was under the bed, between the frame rails (as described by 48 chevy truck dude). Maybe someone knows if the 47-53 panel-body tank is the same/similar?
The 49-53 standard-cab-trucks' tanks were the same style.
The 1954/55 tank had a top-mounted sender AND gas "pickup" tube (but, maybe the 49-53 tank could be used in 54/55).