What Mel said
If your question is actually whether your Aircraft can be considered a light sport aircraft?
The answer to that is it depends.
First, a statement for clarity. An Aircraft doesn’t have to have been defined as a light sport Aircraft., For a sport pilot to legally fly it. It just has to have met the light sport requirements for its entire operational life.
Meaning, that it’s certified gross weight, flaps up stall speed, max. continuous, cruise speed, meet the light sport requirements. Along with it, not having a controllable pitch propeller.
So if your RV 12, with an entirely different firewall forward installation, still meets the light sport parameters then it could still be flown by a sport pilot.