If its for a track car, then do it MR instead, will handle better anyway if properly setup, and is simpler in a lot of ways (he can use existing engine and box and driveshafts etc for example)

But better still for a trackcar just leave the fooking thing alone!
205 gti's handle fantastically in FWD guise if properly setup, so why would you want to convert one to RWD?

Sounds like a dreamer who hasnt thought things through!