I'm installing an M1 Procharger on a 454 mag (carb). The mechanical fuel pump will be bypassed with an electric pump. What should the fuel pressure be at idle ?

You need to call procharger.I believe you need a boost referenced fuel pressure regulator.so the fuel pressure goes up with the boost.At idle no boost reg fuel press. is 7psi

I have upgraded to an electric fuel pump and a boost referenced regulator. I just wasn't sure what the base fuel pressure should be set at.
Calling Procharger is a joke. The goon I got on the phone couldn't even tell me what what size jets I need to start with!

The arb needs to "see" 5-7 psi at all times. Since it is in a box, if you are under 10 pounds of boost, the carb wil need to be FED 15-17 psi of boost in order to still "see" 5-7 psi. Savvy?

So fuel pressure base setting should be 5-7 psi.
And it should increase 1:1 with boost pressure in the box.
1 psi boost = 6-8 psi fp
3 psi boost = 8-10 psi fp
5 psi boost = 10-12 psi fp