Here is the spec sheet for the tank that I used. The tank sits on the hull strake, and is tight under the deck. I had to put a new filler in that is about 2 inches further outboard than the old one.
In installing the tank, I put the tank in, and then put the filler pipe in and the filler deck plate. The filling pipe fitting on top of the tank and the bottom of the deck fitting are almost touching – so do not get a deck fitting that drops way down.
The Moeller 19 gallon tank comes in two varieties: portside and starboardside withdraw. The difference appears to the which of the two long sides of the tank is angled outward and which is vertical. Starboardside: FT1894-1 http://moellermarine.com/wp-content/uploads/pdfs/032718.pdf . vs Portside: http://moellermarine.com/wp-content/uploads/pdfs/032618.pdf . Jonathan Bressler’s boat ended up with this 12 gallon model in the rear lazarette:http://moellermarine.com/…/12-gallon-permanent-below…/
Sailing Tranquility 