I used a SM420 shifter arm like Eric did except that I notched a flat spot on one side to match the flat-sided T5 stub, then drilled and tapped for holding them securely together, them TIG welded them together as well. Makes for a nice originalish look except that the T5 comes out of the floor further back than the SM420 does. Close enough for me.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission