There's a generic brand of EVA foam called Minicell.  It comes in
several densities, thicknesses and colors.  I have a lot of 1/4"
stuff that's used I give you to experiment with   It's a closed cell
foam and I use it for outfitting whitewater canoes and kayaks for
seating and knee pads.  It's very sand-able and can be cut and shaped
to almost ay size.  I also have a lot of scraps of the thicker stuff
if you'd like to play with it.  www.noc.com   would have some photos
of it in their outfitter's store section.  It's about $10 a square
foot for the 3" thickness, but I'll guarantee you once you start
using this stuff, you will find dozens of uses for it.  let me know
how much you need.

Another foam that could be used is the 1/2" closed cell neoprene
foam(also comes in 1/4").  This I use for boat outfitting too.  I
have made numerous air type gaskets with it, but the air box gaskets
might be thicker than 1/2'.  You can laminate either foam with the
yellow contact cement so you should be able to get pretty close on
thickness using that method.

Good luck.

DM&FS

At 09:40 AM 9/1/2008, Evan Mac Donald wrote:
>Sorry about the "no airbox" in the pictures. The pictures were not
>set to the correct "permission". All is fixed.
>
>    http://flickr.com/photos/vdubdad/sets/72157603053264843/
>
>   Anybody got any suggestions for the best foam to use for
> replacing the lost foam in the airbox? Or maybe better, any to really Avoid?
>
>   And for the pictures with the kids under the van with me - out of
> frame in those pictures is a 35,000 lb. capacity ratchet strap,
> hooked to the rear bumber mount, holding the van in place on the
> ramps. It was attached to a BIG fixed object. And the van was
> chocked in place at the front wheels.