First, you must have a certified material that is STC'd or PMA'd for the aircraft. Otherwise it would be a field approval program. There's not a lot of choices out there. Foams are the wave over fiberglass and there are some products that are supported.
http://www.soundexproducts.com/
Soundex is good place to start, as they have 337's listed. I have this material in my plane and I have installed it in another G model. Did it help? Not really but made me feel better that all the fiberglass was out and it sure is nice to work above the headliner now. Much cleaner neat system but not totally easy to install. They send a template with your sheets of material and you cut to fit each cavity.
Aircraft Spruce has material too but you can buy direct from Soundex
There's some talk on my Complete Re-furbish thread
http://www.337skymaster.com/messages...hlight=re-furb