I second the McMaster Carr suggestion. I'm a firm believer in these type mounts/isolators and have been using them for years in all types of applications. (air ride compressors, air ride valve plates, MSD boxes, ECU's, anything that generates noise/vibration OR anything that vibration could harm).
http://www.mcmaster.com/#rubber-isolators/=xkah1c
Look for the "Vibration-Damping Sandwich Mounts"
I like the look of these as they are engineered solely for the purpose of isolating vibration and resonance sources - think aircraft applications. This type mount combined with poly-loc fasteners give your truck a more "thought out" & "engineered" look where the rubber/silicone sheet just stuffed under a noise source looks a bit amateurish and just plain cheesy in my opinion.