I have a 1990 F-350 with a 7.3 IDI motor it did have two fuel tanks, but it no longer does, however the selector valve is still there with the old lines plugged. I want to build a tank for for heating SVO and possibly filtered WMO. My question is can I wire the old selector valve so that I control the return line independently of the supply line. I want to be able to switch back to diesel with out the oil going into my clean tank, so mainly just wondering if this can be done with the stock sector vavle or will I need two valves to achieve this? thanks in advance for any input, this is a great website and has helped me out on numerous occasions.