I did this mod this afternoon and just finished the 2nd shakedown cruise and so far it seems to be working fine.
It feels like its running alot better but it could be my imagination
I'm hopeing it clears up the massive condensation condition thats just recently cropped up w/the cold weather and it should improve engine breathing as I discovered the road draft tube was just about completely stopped up when I pulled it. This engine was barely breathing.
I decided to go the same route as Deve and mount a PCV valve in a freezeout plug installed in the draft hole. Luckily the deflection plate was still in there so it may not suck up too much oil.
Vaccum wipers work and engine performance at all rpm is great & uneffected.
Parts used:
Purolator PV141 PCV valve
42058 PCV rubber grommet
47051 universal vaccum Tee
4' 3/8" gas line
1 1/4" freezeout plug
I spliced the Tee into the wiper vaccum line at the manifold. I measured the grommet where it seats when installed and drilled the hole in the freezeout plug a hair smaller (used a step bit).
All in all it took maybe an hr.
Vaccum Tee PCV valve 
