Rapidash: 108 Speed, provides a nice +Spd Nature with 24+ Speed IVs, it shouldn't need more than that.
Salamence: 118 Speed Neutral, 129 Speed for +Spd Natures, it's only off slightly.
Zapdos: 129 Spd provides a +Spd Nature with 28+ Speed IVs.
If you want any other speed or Endeavor numbers, let me know.
You should definitely do Rapidash, and may be Salamence. I don't think you can reset Zapdos unless you have memory backup, but you can use a speed tester and give it a shot.
If you want I can tell you the Speed/HP numbers so you can try and set it up and save some time.