Like most people I normally take the "it's a proven engine in racing" thing very lightly. That's because most often the "engine" in question is really just the block and no other part in any way resembles anything that will ever be seen on the a production line. NASCAR is a perfect example, Toyota proudly proclaims the prowess of their mighty NASCAR engine, meanwhile that is the only place in the whole world the entire engine exists. Ford however has gone in the exact opposite direction. They went out to see wha they could do with assembly line parts. In the Daytona Prototype engine the only differences were bearing, rings and pistons. On the top end they changed cams and intake but used ported factory castings. They even did all the original testing using a street car computer (later switched to real racing controllers with live feedback back telemetry, more data logging points, higher speed data output......a better computer)
I think Ford is really onto something with this car. They will have to build it for 2-4 years to get 100% into all the series they have talked about. I really hope they stick to it beyond that. I hope they stick with it for a good long time. For any American racing fan there is a bit of pride to seeing one of our much maligned domestic brands go kick the Europeans snobby asses right of the podium.