Andy,
It could be as simple as not getting enough fuel through a single carb although I have seen single carb turbo setups.
This is my setup from back to front:

1. Stock outlet nipple on gas tank removed and a 5/16 inch nipple welded in.
2. ProComp 15 psi fuel pump mounted under car in the back with fuel filter. 5/16 inch rubber fuel line.
3. 5/16 inch fuel line from rear of car to the fire wall in engine bay.
4. Mallory Vacuum fuel pressure regulator
5. (2) 1/4 rubber fuel lines from regulator to (2) Weber 32/36 carbs.
6. Fuel return line from fuel regulator back to the tank using old fuel line. Connected to the top of tank.
7. Vacuum line from intake below the carbs (not connected to the carbs) to fuel regulator.
8. Plastic Floats, 120 jets on primarys and 140 jets on secondarys.
9. Fuel Regulator set to 8 psi at idle.
10. Blow-through supercharger. Max boost 10 psi. Boost gauge connected below the carbs.
11. Vacuum activated Blow-Off Valve. Vacuum hose connected below the carbs on intake.

I use to have leanout until I installed the pump and regulator. Now I get as much fuel as I need.
Each of the webers is running about 300 CFM so a 600 CFM Holley may be your answer.
Let me know if you have any questions.

Thanks.
Ernie