So, first order of business for me is to figure out exactly what the right-to-left shifter conversion entails, so that I can effectively "de-retrofit" the bike.
The bike...

The shifter-crossover mechanism under the cases...

The right-side shift linkage hidden beneath the right cover...

Close-up of the left-side shifter set-up...

Looks like I have to remove the original pegs plus the crossover linkage below the cases, then install the left-side brake rearset with a new, shorter brake cable and kicker extender. Then remove the right-side shift setup and insert the rearset's longer shifter rod in place of the current shorter version.
Anyone on the forum had recent experience with de-retrofitting this type of set-up?
Thoughts, ideas, suggestions welcome. Cheers.
Peter