Try the Daishin Silvia (prize car at RRV/GT Cup), for starters. Anything between 350-450hp should make it fair.
If you've got the dough, and the skill, the RE Amemiya RX-7 and Cusco Impreza should be good for the GT300 and GT500 series.
Welcome to the GTPlanet forums, Thrasher...nice screen shots; your splash page is quite funny, too!