My 78 is missing a hood. I want to get a 2 inch steel cowl but I want to actually work.

Is there a "doughnut" that goes over the air cleaner? Do I keep the air cleaner top on or off when the doughnut seals? Is there a flapper (operated by thottle position)?

 

Cowls will work without anything else if you have the right intake and air cleaner. My intake is tall enough that the air cleaner element sits up inside the round opening in the hood with only 1" of clearance around it. I could build a seal and a new air cleaner base to fully seal it but don't like the looks of them.
Chevrolet made an early air cleaner assembly for 1st gens that sealed the air cleaner to the hood for a complete connection, but they're very spendy as repops, and even spendier if you find an original.
Here's a shot of the inside of my hood:

And here's the 1st gen air cleaner ***. $350:


I built this one for my old setup to seal it, but it looked ugly, so took it off:

 

I have the same hood

I'm looking for ideas too I found this "idea"



from here
1970 Chevrolet Camaro Z28 – Small Block Brawler – 57 | V8 - drag racing, hot rods, muscle cars, car shows - NZV8 magazine

I havn't found anything inexpensive.
Just found this in the "new" section of Jegs

AR Bodies Pro Flow Cold Air Boxes - JEGS


Whoa I just found this (a cake pan) hummm

at http://www.camaros.net/forums/showth...=163966&page=2






again still a bit pricey

 

As I'm looking around I found this Item Part #14HS

Models of Ram Air Box

But still is

Price s/h
14HS Hood Seal air box, w/o filter assembly $129.99 $32.00 $162.00

I'm amazed since I have been looking & could not find any info before

here's another idea (I was looking there but never found this till tonight)
Making a custom air cleaner for steel cowl hood. Ideas? - NastyZ28.com