There are 2 bolts only for the starter motor. If it's the original then it might be very secure with in it's mount. Due to corrosion and a tight fit. Get a wodden mallet and tap fro all directions. It will come out.
thats just a sure indication its been changed in the cars life, because replacement starters dont have the threaded stud for the brace strap. Basically there are two bolts that go down inside the entire length of the motor, on my old motor those bolts continued out past the endcase and thats where the brace fitted to. I just swapped the old bolts to my new motor, so i could still use the brace.