[KeoRS]

Originally Posted by Geronimo '74

They did not.
The V8 comes out of the Cayenne, at most they optimised it, not built by RUF, not by a long shot.

Here is what I found:

From Ruf

RUF Automobile GmbH - News

RUF is proud to present the brand new RGT-8 at the Geneva Motor Show, 04th -14th March 2010. This spectacular prototype vehicle is powered by a completely new RUF designed V8 engine with a 180° crankshaft “Flatcrank”. Four valves arranged spherically together with multipoint fuel injection ensure optimal mixture conditions while the dry-sump system supplies the necessary lubrication. The lightweight engine has a very compact design, has a capacity of 4.5 litres arranged as a V8 and delivers 404kW (550bhp) @ 8500rpm and complements with a maximum torque of 500Nm @ 5400rpm. At all stages of the design process, compactness and weight saving were of priority, the result of which is a total engine weight of less than 200kg. Please find more information in: task-menue - VEHICLES - RUF-MODELS

From Autoblog

Geneva 2010: Ruf RGT-8 is a V8-powered, 550-hp 911 — Autoblog

Over the last decade, Ruf has created two versions of the Porsche 911 bearing the RGT moniker. The first was a 385-hp, 3.6-liter 996 and the second was a 445-hp 997. Now, the supercar manufacturer (don't call 'em a tuner) has created its third iteration, the RGT-8, and it's the firm's most impressive engineering feat to date.

Nestled within the back of Stuttgart's finest, Ruf has managed to squeeze in a 4.5-liter V8 putting out 550 horsepower at its 8,500-rpm redline and 367 pound-feet of torque at 5,400 rpm. The 180-degree, flatcrank V8 is apparently custom designed by Ruf and comes complete with titanium connecting rods, a dry-sump lubrication system and spherical heads. And not only does it meet both U.S. and European emission standards, the whole swap is reportedly 80 pounds lighter than the 3.8-liter boxer-six it replaces.

A custom interior, integrated roll cage, 19-inch Ruf wheels (wrapped in Michelin Pilot Sport Cups) and carbon ceramic brakes (among a host of other mods) round out the package. Although Ruf isn't quoting performance figures or putting a sticker on the RGT-8 yet, we've gotten word that production is set to begin in 2011 and orders are currently being booked. We're buying a lottery ticket in Lausanne right now.