Why do you think that , the kit is made out of FRP (fiber reinforced polymers) , Reinforcement can be fibers of glass/carbon/aramid etc. not your common fibreglass kit, the purpose behind FRP was due to weight redution over steel
The purpose of the kit was for JGTC
The kit was all about properly functioning aerodynamics as opposed to outright speed, with Toyota investing a lot more financially into developing the 3000GT kit than previous attempts, using wind tunnel testing and 3D simulations to gain the best compromise between functionality and appearance.
The JGTC Supra wore the 3000GT aero parts in the final race of the '94 season, which would lead TRD to further hone the aero parts to gain the best performance possible.
You could bring your Supra to Toyota Technocraft to have the kit installed , they offered a conversion service to transform these cars into a TRD3000GT, similar to the ZTune Kitted Skylines and Nismo Omori Factory