I`ve been running a Mallory comp pump ahead of the mechanical for 17 years. It has regualtor and I dial it back to 4-5 PSI before the mechanical pump.
It will pull thru the electric pump if I choose to turn it off, however it runs a lot smoother with both running, and helps a ton with vapor lock and long term storage and start ups..
Car is a stock 440 with Carter Comp. series carb..