How to quiet down my 3" exhaust?

Dr. Charles, I bet I have what you need: 3" Dynomax VT mufflers. We have set on a 408 68 Barracuda and you'd be amazed at how quiet they are for such a short case. No resonation. If you have big cam, you may hear some minor tapping as the valves flutter but likely mounted under the trunk, you would not.