Possibly a Sweep T/Y/U of some sort.

There's some engineering that needs to be taken into consideration with the top though.

First off.... It needs a screen. Birds have tried to take up residence in my truck in 1 day before.

Then, it needs to be designed so that it can ingest rain water going down the road at 70 mph. The Safari snorkle does this by having the water hit the inside of the scoop, and run down, but drain out of the scoop where it meets the tube.

I'd leave the top loose enough to swing around by hand. My scoop got ripped up by some roots on an embankment because I did not turn it around.

Turning it around on the trail sure seems to cut down on the amount of leaves/sticks/pine straw that gets into my air cleaner.