track car....really depends on your budget and how competitive you want to be.
my heart would say import an S202 (because its the lightest of the gd8's, sti parts galore, 400 made so it has that air of exclusivity and you know it works, witnessed by the success it has had in targa tassie) but then, by the time you finish with it, roll-cage,
ecu, diff controller, coilovers, tyres add 15-20grand ontop of the purchase price so it becomes a 60+grand proposition.
i personally think you should buy a racecar already setup saving you a small fortune. frequently visit my105 for the latest offerings as people sell due to upgrading or moving on.
building a racecar from scratch will become a massive financial strain and the older your base car is the more frequent preventative maintanace it will require. a 10+ year old gc8 although still can be very competitive and uber reliable but it is getting long in the tooth and the technology in the later model cars would run rings around it.
check goo-net every so often, usually 10+ s202's for sale at any given time.
s-series for satisfaction!