Hello,
Affolter will tune / modify any model Diablo you like, from the standard 2wd model from the early Nineties right up to the 1999 models or even the VT 6.0.
The Evolution GTR was based on a normal Diablo, not even a Roadster, the conversion was performed by Affolter.
He is rather expensive from what I've heard, but the result is stunning, trust me, I've seen this light blue car in person and was very impressed with the fit and finish of the conversion.
I would rather buy an Affolter than any standard Diablo, either a GTR Roadster or the black GTR LeMans version which is also featured on the Lamborghini Cars site.