It appears to be the defunct
"Powersports" reduction unit. A bit heavy. All custom made parts.
Allows a bit of an offset from the crank centerline, so clearance over the top
of the engine may be improved. And real pricey.
At least two are flying in RVs. If you
did a piece on the "Powersports" redrive then you should have the
data.
I’ve seen one installed in a flying
Lancair ES with a 20B, but we’ve never done an article on one before.