I think you need to go back and read it again, as it was very clear that they have a car already, it just needs re-engineering and WJ is doing the work. From the article:
"I needed some special parts to do the project the way I want to do it," Johnson said. "Because the confines of the area I’ve got to work within the engine bay part of it are really restrictive because this thing was originally designed for a flathead Ford." Johnson estimates the car will make more than three horsepower per cubic inch.
"I’m re-engineering the whole car to make it right," Johnson said. "Maskin and I are going to work on the motor project and I’m going to make the car, well it’s obviously a car that’s very efficient aerodynamically, but mechanically it’s a total disaster, so I’ve got a lot of work to do."