Carburetor is flooding.?

I have a 1978 Buick Regal with a 383 stroker. I adjusted my floats all the way down on my Holley 4150 carburetor and fuel is coming out of the hollow shaft that rises out of the float bowl. When I raise the floats, more fuel squirts out. Fuel pressure is at 5.5 psi. I am uming this 600 cfm carburetor is too small if anything. This problem arose after installing a new single plane intake. What could the problem be?