You can also try one of my shifter gaskets. They really work very well. They're designed to reduce the noise (from transmission) that is transmitted through the (billet) shifter. I am constantly getting feedback that a good percentage of shifter noise was eliminated with the gasket. A few members here have tried it and were pleased. Works well with the stock shifter, too. And no messy silicone sealer to deal with. Here's the link if you're interested. You can also read more about the gasket set. Cheap, too. $5.00 for the T-56 and $6.00 for the TR-3650/T-5/T-45. Shipping is free.
http://stangshiftergaskets.com/index.htm