If you get rid of the crankcase vent/spacer, you would replace it with something like this:
http://www.knfilters.com/vent.htm (crankcase breather filter).
Healthy engines pull air in through this device...but, my engine pushes air out (can you say blow by). Engine still idles great, pulls great, burns a bit of oil (nothing visible while running) so I don't worry about it.
For my truck, the air filter housing will to fit directly on the carb (Qjet) and still clear other engine components.