Definitely on the right track with carb and fuel system. Try to get it to idle in gear even if it's at 1,100 or above. My suspicion is that the carb is losing it's vacuum signal at the lower rpm. The bouncing rods say to me that the carb is sensing an open throttle do to the low vacuum signal and trying to go into the power circuit. My roller cam 400 does the same thing if the idle falls below about 1,000 in gear. With that cam and heads you might be better served with a Holley.