Apologies. You did mention the thing about it being cheaper to do an engine transplant. The problem however is that the Fronte is a fwd and fitting a bigger engine would be more troublesome than if it were rwd.

By the way, the Mazda rotary does not count because it has more power strokes per revolution (I think 6 power strokes/rev for a 2-rotor), so it would naturally produce more power than a piston engine of the same displacement.