Rewriting JAR licence into FAA lincence - NOT validation

I would like to rewrite my JAR licence (PPL) into a FAA licence. I already
have a validation (US licence based on foreign licence). Do anybody know the
procedure? I know that I don't need a regular american licence to fly in the
US but because of some special reasons I try to get a stand alone US
licence. Do I really have to make a complete new PPL-Training or is it
enough if an examiner certify that I have all the necessary requirement and
I have only to make the usual exams?
Btw: I have over 500 hours flight time on different planes.
Thanks!
Astrid