"It is this same line of thinking that the stock regulator somehow is able to maintain proper pressure (even if you install a high flowing pump) that got me into trouble by installing a higher flowing pump in the first place without being prepared for it. It doesn't do that based on what I have seen. If you fit a 400lph pump, the fuel pressure will be too high running the stock reg on stock fuel lines no matter what. Maybe there is something wrong with my setup, but I suspect that is how it would be in any car running the the stock reg."
The "somehow" is by means of a spring. I have a Walbro fed surge tank with a Bosch 044 pushing more than stock flow through my still stock FPR.
Do yourself a favour and do the simple no cost exercise of blowing though your return line before you go to the trouble of fitting a new pump.