Those Holley regulators can go bat Crap crazy. It’s a bit difficult to monitor fuel pressure without a gauge in the car or a data logger to record it.
I'd ditch it completely if I new the carter high flow wouldn't over power the needle and seat in the holley 750dp. (might be worth testing)
Forgot to look at the fittings on the fuel pump before I left home. Ordering parts to ditch the braided line. Thinking its 1/4npt going into the pump. (hard to tell from the pictures I can find)