Just for an extra thought and info for you, I have a full size fuel gauge that I'm able to install into one of my vehicle engine compartments (it has about a 12+ inch rubberized flexible hose attatched) and tape to the windshield to I can go through a full throttle track run and see if there's any variations in pressure. Of course this is on a EFI engine which has a mucho higher fuel pressure.
*As for the question of putting a regulator before/after a fuel filter; it's Not Even a Dumb Question. The regulator should always be placed AFTER the filter. You do not want any varience (like a slowly plugging filter) to vary your fuel pressure. If a filter is working harder over time, that's a variance. The regulator isn't a computer that thinks, therefore it isn't adjusting itself for too small of an injector or a plugging up injector/ think computerized carb / it only tells the injector to stay open 'longer'. Your Regulator is designed to prevent OVER-pressure or to allow more pressure. so if the clogging fuel filter was between the regulator and the carb, you would't know that you had dialed in 6 psi and the carb was only getting 3.75. Make sense? But if the filter was before the regulator, it would pull down the pressure and you would see the results of that visibly by the miniture pressure guage and can adjust for it.
What you can't adjust for is your fuel bowl suddenly running dry or fuel starvation from a severe cornering issue, etc But I'm definitly not a carburator guy. Hope that was descriptive enough. Nitro-Nicky