Okay... Talked to some more people and the idea with the PCV valve to circulate air through the motor using vaccum from the engine, and to recirculate unburnt fuel through the engine.
The PCV valve regulates the amount of vaccum used AND puts the air and gas from the crankcase back into the cylinders via the intake manifold.
The Road Draft Tube sucks the air out into the atmosphere.
With either system you need to get air INTO the crankcase. On the Inline Sixes there is either a 'breather' cap for the valve cover, no breather cap and vents in the cover, or something else along those lines.
An example of this set up is the V-8 350. One valve cover has the PCV valve connected to a vaccum source, either the intake manifold or the base of the carb. The OTHER valve cover has a breather element or another source of air, such as perhpas a line to the aircleaner for filtered air. Many of the more modern carbs have lines in the base of the carb for this reason and which often are capped 'cause they aren't being used.
On my 261 (and any other inline six with a road draft tube) you could put the PCV valve in either the valve cover or the original road-draft tube location for your 'outlet' line. The inlet will be a breather in the valve cover. Or perhaps visa versa, PCV from valve cover to manifold and breather filter in road draft tube location. Either way you gotta have an in and and out.
In the process of figuring this out I have learned a little about PCV filters, which are filters in the line between the crankcase and the intake manifold. These filters leave unburnt fuel in the air but take out things like carbon and suspended oil which, if not removed, contribute to the carbon and gunk build up in the cylinders/valves/etc...
Here is a link to a page I found in another thread with pictures and information:
http://www.condensator.com/ Here is another link, from another thread, with instructions on how to make your own!
http://www.himacresearch.com/books/hydro8.html
