Because the FPR fails in most cases in only two ways, you can be somewhat certain it is working if you have output to the return line, when running the pumps without running the motor.

First be sure some of the fuel isn't being output through a leaky vacuum diaphragm. Check the vacuum hose for signs of wetness and fuel odor. Do this with the motor off.

Then, motor still off, jumper fuses 5 to 7 to get the pumps running. Using pliers with a smooth, flat jaw, gently squeeze the return hose while listening to the flow and the sound of the pumps. If you listen carefully, you should also hear the ball (high pressure valve) seat inside the regulator each time you let the pressure loose, but in any event, you'll hear and feel the return flow to the tank, so no real need to flow it into a bucket.

This doesn't guarantee the pressure is right, but it probably will catch 95% of the regulator failures. If you like 100% certainty - make an adapter; buy a gauge. If this is your only car, just buy an FPR.
--
Art Benstein near Baltimore

Be careful of your tongue: It's kept in a wet place and could easily slip.