Hello Vanagon Types

I have decided that it is time to tackle the firewall insulation in my '85.  Some of it is falling off and it is covering areas where rust is developing.   Has anyone come up with an alternative insulation?  I saw some ideas on another site, ranging from having nothing to using closed cell spray foam (does not absorb water) to fatmat.  None of the posts mentioned long-term success.  I do not plan to pull the transaxle to do this, so using spray foam would be very difficult.

Thanks in advance for any suggestions.

Dave B
Boise