Rob,
I was told that those shifters are made by Buick, and are for the 65, 66 Buick's only, no other GM shifters bolt to the crossmember or are supported by that bracket that goes to the floor brace.
The shifter in my GS is a Hurst competition plus with a Buick handle fabricated to it.
I think your shifter can be rebuilt, I looked at my original shifter and think it can be refurbished with a little of research.
Jay