Before I get myself into trouble, some definitions we should agree on:

'Push Rod' [poosh rahd] N. Metal pin or protrusion located on the interior side of the Power Booster through which the vehicle's brake pedal affixes and is secured with a clevis pin.

'Piston Rod' [pih-stuhn rahd] N. Metal pin located on the opposite side of the Push Rod (see: 'Push Rod'); inserts into Master Cylinder bore, activating Master Cylinder's internal piston; responds to power booster when operator's foot pushes brake pedal.

(Note! Definitions mine, not copied from any authoritative source or manual!!)

The Piston Rod is adjustable by grabbing the pointy end with a wrench and either twisting it in or out depending on the desired master cylinder depth. The goal is to place the pointy end so it touches the rear of the M/C's piston seat without causing it to partially activate (brake drag). The inverse is a shortened rod causing excessive brake travel.

Depth can be 'calculated' (meaning 'guessed' at) by measuring the distance from the base of the power booster's exterior gasket to the inside of the M/C. However, I'm sure there's a better, more scientific way which I know nothing about.

As for swapping from power to manual, from what I understand, a manual brake M/C's piston seat is further outboard than the power brake model. And since I've never done that conversion, I know nothing more about that either.

Not much help, but I had a few moments.