panda-k-bear
I'm afraid you're wrong on both counts about the 737-800.
1) The wing is new.
2) It was certified to the Type Certificate standards in effect at the date of its TC application, which had to be no more than five years earlier than 1997, the date of its initial certification.
Those are the basic rules in effect. Almost no "grandfathering" is allowed in today's certification world.
If you make a significant change, it has to meet current standards.
Most Airbus and Boeing airplanes today are FAA/JAA/EASA certified on virtually the same day as this saves work down stream.
The only recent exception I know of to this generalization is the A340-500. The FAA required additional leak protection to the cargo hold fuel tank to protect against gear failure events and the FAA certification was delayed.