I want to convert my 1987 Mercedes 300TDT diesel wagon to run WVO using a two-tank system, but I don't want to sacrifice the space in the rear of my station wagon. I'd like to install a WVO tank in either the spare wheel well or in the space occupied by the folding third seat (the space should fit a 14 gallon tank). Is anyone aware of a WVO tank in the shape of a either 1) spare tire but works in the vertical position or 2) a tank that could fit in the space used for the third seat cushion(approx. 34 inches x 14 inches x 7 inches)? thanks