Doing the freeze plug trick at the back of the block can cause increased oil consumption, especially with a high mileage engine with some blow by, just like what can happen when trying to do the same modification in a stovebolt six by replacing the road draft tube with a PCV fitted to a freeze plug. There's a reason the factory guys chose to locate the PCV several inches above the block vent port on both engines.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!