Think about the Screamn' Eagle, it eventually became the Ovation III. There were about 15 Eagle conversions, I own the very first one. So it basically changed the IO-500G into a IO550N, mostly by changing the fuel delivery and N cylinders. The rest of the parts list was identical between G and N models.
I worked with Bobby Minnis from Continental and Kevin Surrell from Midwest M20 (he's dead now) back in 2006 to put together the STC for the "Screamn' Eagle" conversion.
(Screaming Eagle could not be used because it was already trademarked!)
My Mooney is up for sale if you're still in the market, but there are a few other Screamn' Eagles out there. Every now and then, one pops up on the Market. Some have TKS, few have oxygen, the Eagle was a cheaper (entry) version of the Ovation and didn't have things like rudder trim and built in O2. Otherwise, its really identical to an Ovation.
I usually file for 190 knots, and if I push it, it will do 196 level at 7000. Faster than a Bravo below 8000, and a lot less maintenance than turbocharged engines. I hate flying above 10,000 anyway. It gives me a headache.
Good luck with your search.
Dan