Running the formula shows 13.7 gallons capacity.

Should be enough, I had a 16 gallon fuel cell that seldom took more than 12 gallons and that was good for about a hundred miles of in-town running around.
Highway mileage got you about 140 - 150 miles between fill-ups.

Go here to see an article I wrote about fuel flange repair - which is, in effect building the whole darned thing except for the tank.

http://www.roddingroundtable.com/for...265&highlight=