THIS is what/how a 427 should sound, it reminds me of what I had in CSX 3183, and that cam might still be in it. I last drove it about 7 years ago, the owner, a member here I believe let me take it for a spin, with my wife who didn't marry me until after I sold the car..
If the link doesn't work, go to the FE forum, go to page 39, and click on DYNO'S 427
332-428 Ford FE Engine Forum: DYNO427's Car At Idle