i have 98 Gs300 also but if you considering putting on 18in wheel you have to drop your car for sure. I had on my car 18in chromed rims,eibach and L tuned shocks. I think i still want bigger rims on it. 245/40/18 should be good or even wider if you have wider rims, i meant 8.5 or wider rims. Post the pic of your car. Let me know if you interesting in 18in chrome i might sell mine lolz.