Sounds like this 67 is not the kind of car you should own!!

This persisted well into the Positive Crankcase Ventilation era,
actually.  My recollection (warning: small-sample statistics dead
ahead) is that the dedicated oil-filler tube came along sometime in the
70s, probably in response to ever increasing government demands to cork
up or intramurally recirculate a car's various vapors.

I'm not sure when Chevvies grew PCV valves, but I think that the
devices started coming along in the early 60s,  supplanting the earlier
"road draft tube" as a means of crankcase ventilation.   (AFAIK the
first use was on the original  Willys Jeep, as part of an attempt to
make it fare better in water crossings.)

My '66 Bird, for example, has PCV (and as a California-spec car was
supplied with first-generation versions of both Air Injection Reactor
and  Exhaust Gas Recirculation) but also a breather cap on the valve
cover, connected to the intakes with a hose, that doubles as the oil
filler neck.

Although I am having trouble finding truth carved in stone on the
subject of when PCV came to be required where, I am taking a slightly
educated guess that first generation PCV (vented breather cap) came out
in 1963 as a 49-state requirement, having been pioneered in California
a few years earlier.  Then in 1986, closed-loop PCV became the
requirement.  I get this by interpolating among
http://www.camaros.org/emissions.shtml
and (with the caveat that some of their statements are pretty
Pontiac-specific)
http://www.firstgenfirebird.org/firebird/FAQ/engine/general.html
as well as
http://www.allpar.com/mopar/emissions.html
and
http://www.harmons.com/catalogPdf/2004/Chevelle/67a83-108.pdf
and
http://www.ajgeneral.com/chevelle_parts/
I'm imagining a three-foot hose with a 90 degree bend molded into it,
and a PCV valve in the valve cover opposite the breather cap.

The implication for the original poster is that there should probably
be a PCV valve in there somewhere.

Finally, there's the great question of all newly acquired vintage cars:
whaddaya got in there anyway?

I *think* (again, I'm not even the sorcerer's apprentice, much less a
guru, on that era of Chevy) that in 1967 only the Camaro got the
brand-new 350.  So I wonder if you've got a retrofitted engine (either
used or a "universal" crate motor).  The 350 was an instant hit and
proved to be one of the truly enduring instantiations of the
small-block, so the earth was soon carpeted with them and they found
their way into all sorts of cars, including some that didn't originally
have a V8 at all, non-GM vehicles, rods and customs, you name it.

In that case, the proper assortment and disposition of smog controls
and other accessories might not be exactly that of a 1967 Chevelle or
El Camino with a 327.  Casting numbers on the block and heads might
help you research what year it's from, just as you'd use the VIN to
find out what the car had in it originally.

Just think of it as one of the interesting and fun parts of the
hobby...

Cheers,
--Joe

Motor manuals of that time were also excellent. How times have changed!