I have a pair of them sitting on top of a 8-71 and they work great. Yes, the tubes that stick out of the side of the carb are boost referencing ports that you run a hose to the intake manifold (under the blower)they asure that the motor does non run lean at part throttle low boost. The carbs come with #5.0 power valves in the primary side and none in the secondary side. Nice carbs but pricey though. From what I know now I would just coppy them the next time could most likely save one hundred a carb or more doing the modifcations yourself. Those carbs went up $75.00 a coppy sence I bought mine.
Bill