Give her a basic dry run, usually some people leave it up on jack stands and run her thru 1st, 2nd, and 3rd then reverse. Set her down and take her on a nice smooth drive on the highway for about 20 minutes or so. Go home and park the stang for a while then slowly break her in. After a day or two go ahead and romp her into 1st, 2nd and so on. Gears are tricky some people are fine by just launching their stang right off the bat with new gears but I belive the rear end can get expensive so better safe than sorry, your call though.