i agree with casey. if you were able to align it without them before, you should be good to at least attempt to do it again. as a last resort you can pick them up. no need to waste money if you really do not need them. if you decide you want the car to 100% spot on alignment, then they may be a good option ahead of time. if "within tolerance" is good enough for you, wait to get them.
I used to have pro lines on my car and it needed camber bolt on one side but not the other side get into alignment.
You don't need the camber plates, just a camber bolt kit, you'll save a bunch of money.
However you have been running without for so long you've probably needed some kind of camber adjustment and your tires are probably worn funny.
Here is amother thing, if you take your springs out you can get the camber plates to replace your upper spring mount, which is not a bad idea because you are running your stock upper doughnut and they will give out eventually and make popping sounds. So if you want to remove your springs you can swap out for the camber plates and increase the durability of that part, plus get camber adjustment.
The caster adjustment is a maybe . The s197 has much more caster built into the suspension geometry than any previous mustang .
if you run the Tokico D-Specs at different settings with more performance in mind, I like the idea of more caster . However extreme caster can have a tendency to make the the tires wear just a little more on the edges during normal driving over time . From a performance view caster is hard to picture in your mind what it can contribute to fine tuning your ride (but it dose if anyone can grasp what it really dose . )NOT JUST TILT THE GEOMETRY BACK...amazing that ford just now added more caster into the geometry.