[Formulajones]

No way to keep the back drive linkage functional as far as I know.

Have done a few of those swaps and currently have a 5 speed in my wife's 69 Z.

I basically have done what Formulabruce explained. I leave the column rod intact and hooked to the swivel down on the frame. I only removed the reverse rod that runs from the shifter to the swivel. Obviously because the modern 5 or 6 speeds are all internally shifted so there is no way to hook up that back drive rod.
I secured the swivel on the frame with wire in the parked position so it holds the column up in the parked (reverse) position and doesn't move. The back up lights are now functioning through a pigtail harness and switch off the 5 speed.

So the steering wheel still locks as it should when the key is shut off, it just no longer holds the shifter in reverse, and it's no longer necessary to park the car in reverse either. Nothing is modified that can't be put back to original.