An Edelbrock 600 is designed up for use on typical V-8's like you have.If it's too rich ,it was bad out of the box,fairly unlikely. More likely,engine vacuum is not pulling down the metering rod pistons into the light load position or the float needle leaks.
With the engine warm and at idle, loosen the screw on small cover for the metering rod piston, the piston should be in the down position, if it pops up when you slide the cover aside, there's your problem.
