'68 Barracuda Notch

I checked both fuel float levels and they appear to be where they should be. I tried to adjust the idle mixture screws as best I could, but the idle is so erratic that it makes finding the highest RPM very difficult. It jumps around 10-15 rpm just sitting there. No matter what I do, the idle just doesn't smooth out. Could my cam be too aggressive (I have no idea what's in there)? The accelerator pump seems to be functioning. My initial timing is around 13°.