Check out the choices at 
http://www.onlinecarstereo.com/products/50/Installation_Accessories/Sound_Damping.aspx?Brand=Dynamat

They have reasonable prices for the good stuff. The light or 1/8 products work well for the doors and front cowl. The front and sliding doors will get you the biggest improvement. Consider the choice of installation. Your car apply directly to the outer skin which stops the cymbal and ringing noises. Inside to replace the door curtain. Or you could do both as I did. The first choice really changes the sound and feel of the doors when opening-closing. Instant Lexus. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Rodgers
Sent: Sunday, May 24, 2015 12:58 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Sound deadening

The time has come when I MUST do something about the noise level in my '88 GL. I seem to recall some discussion about a product at Home Depot or Lowes that works. I'm sure theres others. Anyone know it's name? Any other suggestions as to what to use.

Thanks..

John