Iffluan,
I suggest that you approach your client with a formal request for deviation to allow you to offer API 607 in lieu of API 6FA. I have done this many times and usually there is no issue but, at the end of the day, it is good for both parties to have a formal document accepting the difference. I would argue that API 607 is the more demanding of the two standards and therefore this request is not unreasonable.
I do not believe that it is possible to perform one fire test will allow you to state that you have achieved compliance to both standards.