I've got another data point for you. I just insulated the doghouse with Dynamat Hoodliner, which I installed on top of the existing insulation. This noticeably dropped the diesel rumble inside at the driver and passenger seat.
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2000 Ford 7.3L EB Sportsmobile w/ UJOR
Great, thank you! Addressing the dog house is on our list. It is probably the location where engine noise insulation has the most benefits! But, since the freezer opened here in Montana a few weeks ago, I will wait till spring to deal with it... the glue doesn't like the low temperatures...