Valve cover breathers / crankcase ventilation, Essential???

[The T-man]

Valve cover breathers
crankcase ventilation

Is it required to have breather/crankcase venting?
I have a gen 1 small chevy I am building, and I hate to cut into the custom valve covers I have
could you just do a small vent in the back of the block valley, say 4 an to a remote resevoir, is that enough, or a bad idea?
I see some track motors with a vacuum pump, what's the deal with that?

Will it cause serious problems to NOT have venting?<<<<<<<
any good pics of what you've done please link
thanks!