Someone already pointed you to sounddeadenershowdown.com, pointing out they're closed, but the website still has great info. I was suprised to see that he retired in February. I've used their product for two vehicles, including my 1993 F350 crew cab, which isn't diesel yet but which will hopefully be one by next summer. That site points out that dynamat products and equivalents are only a small part of the solution, and you don't need to layer every inch with it. The main weapon on sound blocking is the mass loaded vinyl, separated from the metal by closed-cell foam, in addition to 25-30% coverage with a dynamat style product. Thing is, it's not cheap. It cost me over $600 in material to do the crew cab, firewall to back wall, plus the doors. But it is now the quietest vehicle I've ever driven, quieter than my '98 volvo. I wish sounddeadenershowdown would offer suggestions on alternative sources for their materials now that they're closed, because their prices were great.