A comment on the valves Terry Kay sells on his site++.  They
are good, brass, Italian valves with fittings that go right
into the hose, making installation very easy.  However,
the diameter of the hole in the ball of the valve is
smaller than the heater hose diameter by quite a bit.  So
it reduces the flow.  That affects the front heater in
very cold weather.

++ http://community-2.webtv.net/VanStuff/VanagonWestfalia

Richard