That's pretty damn weird. 28-32 pitch props and they all run 73. Not sure what to think of it. I would say though, do not run the 32. If your only able to turn 4500 rpm's, your lugging the motor too much. This causes a greater chance of developing detonation. Also it's harder on the drive. Run the 30 pitch and let the motor rev out a bit more. Easier on motor, easier on drive and gives a better mid range punch.
Darrell.