I don't know if my observations on the 69/70 central oil tank (S and Roadster model) will be of help, but on my central tank, the tube from the timed breather on the left side of the engine goes to the top hat thingie spigot, or in later 69/70 oil tanks right beside the top hat thingie spigot. The central tank had a breather internal that went into the air filter and came from up inside the top hat; the 68 Fastback, and R model did not have that arrangement, so I really can't speak to that but I bet it's similar somehow.
However, if you look into the tank, the line from the timed breather should just dump into the oil tank, and there should be another spigot? that probably goes into the air filter or maybe off into the wilderness that comes from a line that ends up inside that top hat, maybe there was no pollution control in 68. Not sure.
There's no problem venting the oil tank (proper) breather into the air, but be careful where you point it, oil will be coming out of it at some time. I chose to vent my oil tank into a catch bottle and haven't been happier with the lack of oil spreading around. Oil is worse than horse s**t, it gets on everything including your boots.
I can supply pics of the 2 early central oil tank variations if anyone is interested.
Dave
69S