'71 Power Brake Booster Check Valve (and thermal sensor)
Basically, booster just gets connected to manifold vacuum, and the other port gets plugged. My pic from the '71 manual shows the same config as yours from the '70 manual. Here are the pics associated with your question. Here's my booster for my '71. The green tape fitting gets attached to manifold vacuum. PM me if you need clarification
So the line that is connected from the booster to the carb base shouldn't be there. I think that fitting on the carb base gets attached to the heated air sensor (yours looked blocked off) underneath the breather. When it's cold, the sensor opens and allows vacuum to the trap door inside the breather snorkel directing warm air from the stove (tin shroud on exhaust manifold).
Basically, booster just gets connected to manifold vacuum, and the other port gets plugged. My pic from the '71 manual shows the same config as yours from the '70 manual. Here are the pics associated with your question. Here's my booster for my '71. The green tape fitting gets attached to manifold vacuum. PM me if you need clarification