Here is a picture found on the net showing the bottle behind the battery. It is more concealed when you use it on a 68-72, as all you see is the neck poking around the corner of the battery. Very factory look for anyone that doesn't know it doesn't belong there.
EDIT: image not working for some reason - go here and look at pictures of engine compartment on this car.
http://www.ebay.com/itm/Chevrolet-No...m=391383574024