87 F150 with dual tanks. The front tank keeps getting filled from the back tank. Thought we had it fixed due to some crossed lines but no such luck. The front tank got so pressurized that it looked like it deformed the bottom of the tank. I do know the front tank vent line is plugged. The only thing I figure could cause that would be the high pressure pump pulling from the back tank and sending the fuel to the front tank (bad selector valve?). We had gas spewing out the fill nozzle like crazy.
Anyway, I read somewhere on one of these threads about a selector valve for single tanks that had the reservoir with it. Can anyone tell me where to purchase one of this as I'm now planning on going with the single tank setup?

 

This is a long shot, but perhaps check at your local parts counter for a selector valve from a similar vintage shortbox/regular cab, as these only have one tank. I've got such a SWB F-150 and it appears to have the same plumbing as the dual tankers, just with one tank and the selector switch in the cab deleted.