you should be fine, your stock computer "should" pull enough timing on its own, just make sure you dont have platinum plugs ore youll melt a nice hole in your piston. now this is assuming the mustangs have the same leway a LT1 Fbody does, you can make a LT1 eat a 150 shot all day with no timing retard box. you should even be ok on 93 octane, but id run 100 just to play it safe.