The calculation for HP to pounds of fuel is universal not a short cut it's just the physics.
1 HP = 2545 BTU’s per hour

Gasoline is 5.92 lbs per gallon
Gasohol is 6.1 Lbs per gallon

Flat head ford is rated at 49% Therodynamic Efficiency and BTU per pound is based on that .
Modern engines run from the factory at @76%.
Theoretical 18000 BTU per pound of gasoline is based on 49% conversion ratio.
Stock 1979 and up engine is @76% or 28000 BTU per pound of gasoline.
Rings valve seats and throttle plate sealing provides 80% on typical modified engine or 29000BTU per pound.
1 LBS of fuel on a modern modified engine should produce 11.4 HP
Parasytic Loses valve springs, piston skirts, oil pump timing chain ETC lower the net power.

pumping 130 Gallons of air and 9.16 Gallons of fuel on that motor will yield 335 HP


C2500s engine build is the Super Chevy magazines Test mule for carboration and the same build is typically 450 HP.
These motors with carb are routinely dynode with 650 and 700 CFM at 450 HP

As far as your results I understand you are commanding the injector to open and close.
Have you put a scope on the injectors them selves while running and confirmed that you are getting the actual commanded on period.
I alter the ignition with CDI after the module and give a solid 5v pp signal to the reference line.
I get @7400 rpm no load at 4ms on 65/68 TBI injectors
I have seen refurb ECM with cheap slow Mosfet installed could be a slew issue rather than injector flow.

In example I had a 1995 Impala/caprice with 1996 LT-4 Corvette, Radically ported iron heads 280cc intake runners, 194/160 with orange ZZX Beehive springs, 1.6 roller rocker crane rev kit lifter springs, .575 intake .560 exhaust 117lsa cam, SPO timing chain on steel gears, Low RPM water pump drive, HyperUtetic Pistons with tungsten Disulfide coated skirts, Rods drilled with piston squirters, copper shim head gaskets final compression ration 10.8 : 1, HMV55HV millings with 5W-50 oil, oil cooler trans cooler, 4L60E with 4.3L convertor, truck low gear spray, Steel drive shaft GM 10bolt 3.73 with Eaton Posi.
TH ignition system was/ is triggered using opti spark pick up CDI box and twin coil MSD coils. Ford 4cylinder ecoboost injectors in sequential mode rather than batch.
Routinely ran at 7500RPM and even peeked it a few times at 8500rpm.
According to iPhone pocket Dyno and Cats Tuner dyno hit 600HP on regular basis.
Never drag raced the car just street racing.
Have driven the car at Taledega at over 180MPH and at Daytona over 160