Corvair Engine

Here's what's going on the firewall:  a converted Corvair engine, courtesy of Mr. William Wynne.

Note below the Wesseman 5th bearing (pretty silver gizmo behind the toothed flywheel):  it helps isolate any side load from the prop from the main bearings on the engine. Part of what makes it airworthy.  

Just looks like an airplane engine, doesn't it?

Made from a 164 LM corvair engine. Rated for 100 HP at 3100 RPM - both significantly derated from the auto application which accounts for a major safety margin.