Your 67 has a closed positive ventilation system, plugging the hose is not a good idea you may build up too much pressure in the crancase system and the valve cover breather without a tube that runs to the air cleaner will not be adequate. It's not that difficult to come up with an attachment to the air cleaner. My 68 does not have the tube that runs from the back breather, I use a K&N open air cleaner setup but I have retained the factory ventilation system which uses a breather cap with tube to the air cleaner, modifcations were relatively simple
I will post a pic of the setup in another post.