My Bullitt could destroy Coyotes at will but it was pushing 14 lbs of boost on a built motor with ported heads and big cams. That said, the new Mustangs are twice the car of the older Mustangs. If you have any doubt or hesitation whatsoever between building your current car or upgrading to a new one, I highly encourage you to go test drive a new one. I would have preferred keeping my old car simply because it was a Bullitt but for an average GT I'd upgrade in a minute.
Fewwww....... that last statement saved me there! LOL