filler cap question

i have a 65 plymouth fury lll with a 318

just want to be sure i have the right cap in my fsm it states a closed vent system in one figure or a open system how can i be sure the cap does not have a tube on it to connect it to carb yet from the carb to no where is a hose connected to nothing. also the air cleaner has no hole in it for a hose to fit into.im stumped.:doh:
Author: t65fury3