I paid a 11k for a series one 250GT. Okay it only makes 158kw but they're not a slouch. What you will be thankfully for buy a 250GT over the rest is for the fuel economy, it demolishes the rest. I got mine down to 9lt/100km.
I was at Nagoya the other day (elgrand city that place is) try Japanese Motorsport direct in Sydney aswell, they guy who runs it is a deadest champion and the guy who sources the cars is Japanese so he know what it says in all the descriptions on the auction slips and what not.