Regulator is part of the fuel unit (pump, gauge sending unit, regulator) in the tank.
Schader valve on passenger rear of intake manifold.
You can't tell 100% what is wrong by measuring fuel pressure when turning the engine off. The pressure will fall to zero within seconds or minutes; doesn't matter. What matters is that the fuel line doesn't drain all the gasoline back into the tank. So the "real" test is to shut it off, then come back after hours or overnight, with the gauge still attached, and crank to start. The pressure (if the fuel line is still full) should jump to ~50psi immediately. If not, the pump is refilling the line because the regulator let empty.
Really, the engine should start with a poor pump, although it may run rough. No start means no fuel. Otherwise, a poor pump should not be able to keep up with full load demand. You'd have to measure pressure at WOT. A questionable result could still mean a plugged up fuel filter, not bad pump.
