[Shotimes] JBL subwoofer

[van Oss]

With advice from Gil Shoemaker and parts from Al Fitz, I am retrofitting JBL
into a car that came without.  A question about mounting the subwoofer to
the parcel shelf:  The sub housing has four studs on top that fit holes in
the steel.  Surely there must be some sort of rubber washer or other
vibration isolator at these four mount points.  What was used at the
factory?  Anyone who has parted out a JBL, what should I use?

Also:  I have read about people getting fresh foam around the subwoofer.
What's that all about?

Thanks.

Joseph van Oss