I used a 3spd stock car shifter from speedway motors and made some linkage with small heims and links from Speedway as well.
Like this one: 49.99
http://www.speedwaymotors.com/3-Spee...fter,1929.html
I have also seen some people use two stock shifters on a longer pivot bolt and some heat/bend of the sticks.
Mine:
(Please ignore the gloopy seam sealer, I swear the welds under it are pretty. And it took a lot of work to undo the previous owners cover cutting and to fit the NV5600 in there.)