This kit was a custom-made kit consists of LS430 calipers that have been painted red, custom brackets, pads, GS brakelines, Supra TT rotors.
It should bold on a Supra IV, but cannot use the 310mm rotors, unless different brackets are used. But why should you?
If you have the Supra 4-pot caliper, then you have 324mm rotors, and then it will fit.