Pat and Zray have the right ideas.
The Autometer isolator is the only smart thing to use on a street car. But you really only need to know what the demand is when wacking the throttle to redline. You want to see your pressure on demand be 5 1/2-6 1/2 pounds. (Webers less of course) At idle, you only want to see a steady supply at similar psi.
When you get your feed system supplying that, you delete the in-car if you don't care for the look 'cause you just don't study that gauge like
oil press and water temp. Then the underhood gauge is fine for occasional tuning checks.
Mine is at the end of the fuel log:
