Route crankcase breather after air filter?

I don't see why you couldn't, but from what I've seen on my Magnum engine, or any engine for that matter, is oil contamination from the P.C.V. system into the intake. I run an oil/air separator (Summit & Jegs has them) on my P.C.V. system, (a cheap one can be bought from a Home Depot type place, one for an air compressor works, & plumbed into the system) but I also have an open element breather on mine. You might want to think about using one on the crank case breather too. You'll be shocked at how much oil goes into the intake from the P.C.V. system alone. That's my 2 cents.