I think it would be better to go with aftermarket sliders for a few reasons..
You can't set your own angle with those. The mounts on the FJs are huge, I'm not so sure if they would even work because of that and also clear the rear LCA mounts and/or the body mounts and rocker panels. If you wheel it, you're going to probably want kick-outs (I can't tell you how many times I've already used mine to pivot around rocks when there is no room to steer around). I had Trail Gear sliders without kickouts before my 4xInnovations sliders and I have dents and scrapes on my rear doors to show for it. The OEM FJs look short, to give you reference, my 4xInnovs are 66".