Take a guess where the bottle neck is!

Yeah, I had valve float make a car fall flat on it's face. Stiffer woke it up.
If you are sure you still have fuel pressure, look into that. Back in 1970, I had a Duster 318, 3 sp manual, open 3.23, f70x 14 tires. Ran 16.80. Slapper bars to even traction, 16.60. Holley 500 cfm 2 bbl, 18.5., but started falling at rpms. Installed stiffer than factory springs, as I could feel, and see tach not going up. valve float, I thought.
After that, 16.20's.