Manual shifter mtg brkt versus legs or standoffs.
Another solution would be to weld four thin steel plates of suitable lenght and height to the collar setup effectively creating a lightweight steel box. It would be simpler and easier than machining large diameter standoffs and prvide much more rigidity to the installation. Though not an engineer by trade I've taught myself to think like one through many years of devising simple yet effective solutions to the small recurrent problems the Delorean's engineering has presented me on a regular basis over time.
Rob