GMONIZ adds, "the oem gas tank was either a 16 gallon or 18 gallon"
inches: 31 long 11 wide 13 deep = 4433 cubic inches
4433 cubic inches = 19.2 gallons
Drop a gallon for dimples, bends and rounded corners, 18 gallons.
Smaller tank is 6 inches less in length, about 5 gallons. This would be the duplicate "13.5" gallon tank, or simply 13 gallons.
Never been able to pump more than 12 to 13 gallons into my small tank, obviously I cut it close on gas quite a few times.
Don't know about a 16 gallon tank but I am sure one was made, if anything to confuse people half a century later!
Billyray
