Has anyone installed a viewfinder on a Super Graphic?

Where did you locate the screw holes?

I am assuming there are instructions somewhere, because I've
seen them for other model Graflex press cameras.

The optical Viewfinder for the Super Graphic has a different mount from Pacemaker Crown and Speed Graphic cameras. The Super mount is a straight piece with two screws. The Optical Viewfinder service manual list them as "screw-machine".
The Super service manual shows a battery insulator with two holes under the top right side (shooting position) that appear to align with the position of the optical viewfinder on my Super Speed which is buried in storage at the moment.
See https://graflex.org/helpboard/viewtopic.php?t=7020 for the service manual. The IPB section, manual page 52 item 6 is the insulator.

There is no diagram for the optical viewfinder foot mounting in either the Super Graphic service manual or the Optical Viewfinder service manual. They were likely mounted at the factory or a regional service center and the template lost to history.

Thank you for the references!

The screw holes are 32mm apart. This looks very close
to the holes on the battery compartment top.

The screws are 3/8" long, with a counter-sunk, flat-top,
phillips head. They are 40 tpi, but are too big for 4-40,
and too loose for 5-40. They would be a snug fit for a 4-40
tapped hole.

Likely a #3-48. Take a look at https://www.engineersedge.com/screw_threads_chart.htm
The pilot hole is always smaller than the taped hole.
That screw is called a flat head. Its for having the head flush when installed.