What Pontiac did do at the factory is add a thick insulating liner to the convertible well material to some 1st Gens.
To date, I have not found a repro replacement for that liner. I have spent hours and numerous inquiries to convertible top specialty vendors trying to find a suitable replacement material.
Also, I can find no documentation that shows which cars got that extra insulation other than in the 1968 Pontiac Sales Manual page Q-2. In a section describing "Special Acoustical Features.", they state: "Certain 1968 models have added acoustical features to enhance ride, comfort and quietness.".......and...... Convertible also have a heavy cotton-fiber lining in the top storage well to muffle out noise in that area."
That liner was very fragile. As mine crumbled into the trunk during the daily driver years, I finally pulled it off the thin liner and discarded it.
Thank you for the information, Jim!!! I was surprised when I saw this item, below is the verbiage in the catalog on page 274 of the current catalog
These new headliners are designed for use on
convertible Firebird models not originally equipped
from the factory with an internal headliner. Once
installed, this ready made headliner will greatly
improve the looks of the interior, cut down on noise
and help insulate against extreme temperatures. The
top can be raised or lowered without removing the
headliner. No special tools or knowledge is required for
installation! Manufactured with plush Velour materials.
RCH10 1967-69 black ................. 199.99 ea
RCH91 1991-92 black ................. 179.99 ea
RCH94 1994-95 black ................. 179.99 ea
