I dunno the brand name of the spray on bed liner stuff but it's very thick and should help reduce interior noise as anything that dampens out vibrations & reduces ' drumming ' of sheet metal
helps a lot - I glue pads inside my door skins and cab for exactly this reason and my '49 is very quiet inside in spite of it being a rattly old POS .

-Nate
There is no problem so difficult it cannot be overcome by generous application of brute force & ignorance