If it’s the original G3 Lite, you will be limited to units that mount through, or
Over, a normal 3 1/8” instrument hole, or you will need to do some surgery to your panel.
I replaced mine with Dynon and never looked back. I sent my Blue Mountain parts and pieces to Stien. He had some customers needing parts to keep limping those systems along at the time, but that was long ago.