What heat insulation product to use for Duster interior?

Hah. I should scroll more often. That's a very nice clean install. So you used 1/4 inch then? It doesn't seem too costly, that company also seems to have a local office/warehouse so that's good too.

This weekend I hope to start prepping the interior for some dash paint, and primering and laying down some Fat Mat. I won't be able to do much since I'm going to the Roaster Show on Sunday.

Yes 1/4". I used 3M spray adhesive to bond it to the acoustic mat material.