It will not be possible to shoot 1080p @ 60fps with the 70D in camera.
If you put it in 1280p at 60fps, then there is no 3X crop.
Without the crop you will get limitted by the camera max. res. which I am not sure for 70D, but its less than 1920x1080.
If you put it in 1920p at 24/30 fps and try to override fps to 60, you find actual fps is less than 60 fps.
So there is no way to do that. Best bet is to shoot, 1280p at 60fps with higher bit rate, then up res. to 1080p.