Are you looking for an actual 427 used in NASCAR or built to the same specs? Or are you looking for a high performance, correction, an even higher performance
427 SO. If you are looking for the latter there are several builders that can build FE's to your specs. Bill Parham has been working with them for over 30 years and can build you whatever you want. My dad went with him (Southern Automotive) for our 427, so he is the first name that comes to mind. I am sure other companies such as Gessford Machine, or Shelby American could build you one hell of a motor.