Larry Henney's thoughts about the prop cable is worth checking.

You might also check the amount of "cushion" available in the control
cables. The "cushion" (as I call it) is the travel left over IN THE CONTROL
once the controlled item (throttle, prop, mixture, etc.) hit its stop.

For example move the prop control to max RPM. Remove the control cable rod
end from the control arm at the governor. Move the prop control knob in the
cockpit all the way in. You should see control cable rod end move at least
an eighth of an inch or perhaps a little more beyond the postion of the
governor control arm.

ALSO ..... I had a Bonanza not too long ago where it APPEARED that the
governor was hitting the max RPM stop but in fact another part of the
linkage was hitting part of the airframe. I had to re-index some parts to
make it all work but that was the reason it wouldn't hit rated takeoff RPM.

Given that you have new engine, prop, and governor I have to believe you
have an installation problem.

Let's us all know what you find. Good Luck.

Ted Stanley - A&P-IA