If you want to eliminate the stock air cleaner setup, an alternative way is to look for the stock setup used on '85 300d and 300sd delivered to the California market with a trap oxidizer. These used a smaller air filter housing mounted behind the right headlight.
See post #14 here:
http://www.peachparts.com/shopforum/diesel-discussion/214330-1984-1985-different-air-cleaners-300sd.html
Admittedly no points for elegance.