You should have a similar air cleaner to the 300TE I have (different fuel system, though!). On the TE there is a rubber mount, 10 mm nut, in front, one at the rear, and one on the side toward the driver's side fender. Yours are probably in a different location, but check for them. Always a rubber mount that has a nut holding the air cleaner down.
My old 72 280 SE also has a couple of rubber rings that loop over tabs on the air cleaner lower housing and on the manifold.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!