While underthe van getting all the engine stuff hooked up, I decided to put
an on/off valve in the big hose from the gas tank to the filter purchased
from the hardware store.  Used 3/8 brass barbed fittings and the valve hole
looks plenty big enoguh to flow gas down into that small plastic line after
the fuel pump.  Park in a nasty neighborhood, just squat down and reach
underthe car and switch it off.  if someone decides to make off with the
van, it will likely not be far away once the fuel starves.  total cost,
about $9.  Dobles as a gas flow shut off when changing pump or fuel filter.
i hate pinching fuel lines!!

Dimwitted Moose and Flying Squirrel