AFAIK, the IO360 is not approved for Mogas, neither any of the Mooney airframes. Whoever flies a Mooney with Mogas is doing so at great risk, in my opinion and I won't recommend it. Repairing a certified aircraft engine is extremely expensive - ask me, I've just been through that and if your engine does fail as a result of using Mogas, the insurance is also going to show you the middle finger.
Contact Horace wrt Mogas STC. He'll be able to give you the correct answer.
"An airplane might disappoint any pilot, but it'll never surprise a good one." — Len Morgan