I have made over 600 HP with stock rods built like my above post and turned it 6000+ RPM With out any problem.
Sparks cam should rev to 6000+ on a 109 lobe center, this is not a not a low RPM cam that is why it needs a low gear rear ratio.
Plus when an engine has low torque is needs to rev to make any HP that is also why the low gear.
