The 'dummy radio' that comes with the simulator you are buying will hook up to your Futaba radio. You can use your sim radio as the dummy, your instructor will use your Futaba radio, so you have everything you need, plus you will already be comfortable with the buddy box since it's yours

I used my Futaba radio for my sim (actually I think you can do that too, I think...) and when I used the box that my club had, it felt totally different to me. It will be nice to train on something you are a bit familiar with.