Try contacting my old mate Miguel, email@example.com
He acted as adviser for Tokyo Drift and bought all the cars once the filming finished, I think he bought three or four Veilside's and last one he kept was the real real one with all the right mods.
He not only sells cars but he may be able to connect you up with previous owners, tell him Clive says hello.
As you say, it will be cheaper to buy and when you think of the price of the kit,having the conversion carried out and all the correct mods/ engine fitted your probably the wrong side of 50 K to have this done professionally, plus a year to build!
Hope this helps.