Bob,
Thanks for the info.
Airflow Performance suggested a Tee instead of a selector valve,  after the
L and R Facet pumps with their filters,  then into the header.
Then a shutoff valve.  Then to the screen and the boost pump.  With rudder
pedals on the right there's not much room for the boost pump.  On to the
engine driven pump, and then on to the Bendix servo, and up to the flow
divider, et.c  Any suggestions there?
Terrence