Before PCVs, venting was provided by the
oil vapor tank, commonly called a puke tank (a puke tank is also what you set up to catch overflow from your cooling system, especially at the track). The vapors were drawn out by a road draft tube (runs down to hang down into the airflow near the starter)...the remaining
oil would drain down to the pan. Old grey beards like myself will recall the
oil stain that ran down the middle of the lanes on a road before PCVs returned the vapors to the engine to be burned up. Old school...and it works perfectly (and has for the dozen years I've run the tin can on the track and on long cruises). Mine was set up by the boys from Provo to be as original as possible. I do not run a PCV...I prefer to leave my stain on the road. I also like to run gas through my engine, which is not a diesel.
Here's a simplistic drawing...mine also has a tube connected from the rearend and transmission (via a "T") going into the tank via another fitting next to the one from the engine to draw the wet vapors from those sources as well.
Here's a pic of the road draft tube fitting/hose and the oil tube running down to the pan.
Here's the intake side of the tank...the tube connection on the right hand side is the one coming from the rearend and transmission.
As we like to say at Gasholes...
hope this helps with your build.