I used a 24" square piece of Dynamat in the center of the roof and then covered the entire cieling with the foil faced "bubble wrap" stuff for insulation.  You can see the foil stuff in this pic.  I have not yet installed the headliner.



The Dynamat is self adhesive, and I used 3M spray adhesive for the foil stuff.  The dynamat completely removed the "drum" effect of the roof sheetmetal.  Before, I could tap the palm of my hand and it would ring out like a big bass drum.  After, it is solid with no reverb at all.  The foil stuff helps with the sound control, but is really better for insulation.

Pete

Why not use spray-on undercoating from a rattle can?  If you figure that you need more than that, use it for the adhesive to attach other material.

Edwin....either carpet padding ,foam or anything similar should do he job ,it is mainly there as a sound proofing material to stop the drumming you would get if  nothing was used. just be sure you use a good adhesive as the heat on the top can cause some adhesives to let go.

Edwin,
On my 1940 Plymouth P-10 Business coupe I used carpet padding.  I know it isn't the correct item to use, but it fit my budget and works well

I used GE Silicone 2 as the adhesive with no problems.

Hope this helps,
Bob

I am researching products for the headliner replacement on a 50. I don't know what kind of padding to use under the new headliner. The car originally had what looks like paper bags containing cotton padding. I am considering 1 inch thick foam, but upholstery suppliers don't have any recommendations for headliner use. I would like to hear what others have used in this era of Plymouth: how thick, what material, and source. Thanks for your help.