How To Measure Fuel Volume.

I have about 15 runs on my street/strip Duster with maybe 350-380. HP, 3200 (actual) convertor, 727, 4.30 gears, and when I last ran it, 26" tires (It has 28's on it for the next trip.)
Only about half the runs were any good because of shifter problems. I shift it at 6k. I haven't gotten a good read on what it traps at. (See below. The laziness seems to make it vary a bit.)

It runs 11.80's @ about 109-110. It doesn't pull hard at the top end. No ducks, just seems to give up some. I think it should run about 113. (3000# at the line.) But I don't know.

Valve springs seem okay. It revs fine in 1st and 2nd. The pull just tapers off in high gear.

I'm looking through my fuel delivery. I have 1/2" (-8) line from the sock to the Blue Holley pump, through a Fram HPG-1 filter, and up to a Holley regulator on the inner fender. From there, it's 3/8 (-6) to the 750 Holley vacuum secondary (lightest spring) "Street Avenger" carb.

I checked to see if it was pulling vacuum in the traps, and maybe closing the secondaries. I have also checked for full throttle.

The float levels are okay. Fuel pressure shows 6 3/4 idling, a little over 6 in the traps.

To my question: How do I accurately measure volume? I know to pump it into a bucket. The easiest and safest way would be with the engine off and ignition disabled. Would the pump be putting out enough without the alternator putting out the 14.2 v it puts out when the engine's running?

What's a good flow per minute?

I'm also going to compression and leak down tests.