Many thanks for the replies.
There seems to be a wide range of offset shifter options available.
In one end of the spectrum, an offset shifter is just a customized external base bar (@scarebird could you please show some pix of your solution).
And in the other end, it is an internal customized shifter that even isn’t necessarily a bolt on part (like the STX shifter
https://shiftsst.com/blog/post/gm-a-body-1968-1972.html).
Anway, what I am looking for is a bolt on shifter (and be able to buy just a transmission instead of a +$1500 package).