Idler Arm bushing differences Manual, Power and Quick Steering

[6s1640]

Hi all,

I am putting a new bushing into a original GT350 XRR quick steering idler arm.  I have learned that the standard manual steering arm uses a different bushing than the power steering arm and the two have different out side diameters, with and without teeth.  See images below.  Also, the GT350 quick steering arm utilizes the larger OD power steering bushing with teeth.   I have several questions below.

1)  Why does one bushing have no teeth and the other has teeth?
2)  Why the difference in size?  Just to make one arm manual and the other power?  I believe they are the same length.
3)  Why does the GT350 manual quick steering use the larger power steering bushing with teeth?
4)  What actually moves when the idler arm rotates.  Does the rubber flex?  With the teeth, I can't see the inner spacer with teeth rotating on the support arm.

Thanks

Cory