Best climb rpm

MAX power and Max Climb Performance will be at 5800rpm and WOT.

5800rpm at a reduced throttle will always be less Power than 5800 at WOT.

It is not about RPM or Torque or Manifold pressure.

It s about All Three at the same time.  POWER!

5800 at WOT at Vy is what you are going to need every inch of the day "Mr. Density Altitude" comes to visit and you find yourself 10 ft over the treetops and climbing at less than 10 ft per minute.

Paul, search the topics on propellor pitch/propellor testing on this forum by Roger Lee. He has done some excellent testing and research on this topic with various propellors. I would caution against running close to the 6000 rpm in the climb it won't leave much of a buffer for other areas of operation. The lifters can start to float and cause serious engine damage at 6200rpm. See section 05-50-00 in the line maintenance manual for unscheduled maintenance checks.