Is this D-C Mooney conversion done under an STC and the original airworthiness certficiate, or is it a remanufacturing of the airplane complete with a new airworthiness certificate? If it's the former, I'm pretty darn sure the data plate remains the same, just as my Tigerized Cheetah still has its original AA-5A data plate. Every Cheetah-specific part has been replaced by Tiger parts, but it's still an AA-5A to the FAA -- just heavily modified.
Where that gets to be a problem is when I'm adding something else, like the K&N Challenger air filter, where I had a heck of a time getting the supplier to give me the right part and STC for my IA to stack on the STC's already installed. Those familiar with Tigers and Cheetas will realize that a Cheetah air filter does not fit in a Tiger's induction system. The supplier was not happy about sending me a Tiger part to go on an airplane with serial number AA5A-0856, but eventually, I talked them into it.