Ruf being their own manufacturer=being unique to Porsche, which they are. So this unique manufacturer is a good substitute??? right that makes sense.
The only cars that Ruf manufacture that share an exterior resemblance to a Porsche counterpart are the 3400, R Turbo, BTR, CTR, RGT, RK and RT12. that is less then 10 cars out of the hundreds of Porsche road and racing cars or say around 5%. And this is still only an exterior/superficial resemblance.
The RGT is the closest car that somewhat resembles a Porsche in both looks and performance. but it is just a 911 Carrera chassis with comparable power to a 911 GT3. The engine, suspension, breaks and tires are all different. These cars would drive completely different.
There is no Ruf that performs like a stock Porsche. They only bare a superficial resemblance. A car that performs like a Porsche but looks different would be a better substitute in a racing game......unless you just like to look at the cars.