There are TWO factors. Pressure AND volume. As said the Weber wants 3.5-4. The stock mechanical pump gives 5.5 PSI. Don't know volume. If the pressure does not blow the needle valve and the volume keeps the bowl filled, you don't need a reg. Maybe you tried it without already? I don't now if you are building a dragster or what. But the stock carb and stock pump will run a 6 just fine. When you need a regulator you either have injection or are trying to match mismatched parts. Regulators can cause problems with volume, have leaks, go bad and a good one is expensive. Then of course you have to have AN fittings and SS hose and.....
The entire WWW, started by Al Gore, says a Weber 32/36 runs perfect with a Cater 4070 electric fuel pump. $65, high volume, 4psi.
Or put the Rochester or a Carter on with stock pump. Either way is not a mix-match and no regs.
I don't know your history but if you have an Offy intake, a hot cam, EFI and all that, then it's a different story.
