I went with the mechanical switch AC Delco # U858, Napa SL128.

Find the rough position which puts the switch arm behind the pedal arm.

Mark, Drill, and mount the switch to the master cylinder floor pan cover.

Attach brake switch harness and test for continuity across the leads. I removed the douglas connector shells from the harness before this step.

Re-install the cover, ensuring that the switch arm is behind the pedal arm.

End result of the switch in position.
