Which design SPAD is it? If it's a scale ( corospit, SPADstang, Corsair) or 3D (Spa3D, Edge) I'd use an OS FS 70 (more RPM, bigger prop) If it's a Hell on Rails, or a sport, I'd use the Magnum (less RPM, steeper pitch prop)

... As far as a $400 engine on a $10 airplane, the $10 airplane can last as long as a $400 engine. I've planted many SPADs ... 20 minutes with a hot glue gun and a bottle of medium CA, and I'm back in the air...