You have a turbo 400 in a 66 special? They came with an st300 2-speed auto. (powerglide). If you have the original 300 ci (wildcat 355) then you need the linkage from a manual trans skylark, which is more conventional (chevy like). If your car has a 401 (nailhead) then you need 65-66 GS specific linkage. Pedals should be the same either way. Parts are hard to find, and it might be easier to pursue a hydraulic clutch actuation set up. Any way you look at it. The way to approach this , is to find a donor vehicle, that is equiped with the manual set up, (and has the same engine as you ) then swap everything over. Good luck!!
Frank, South Portland, Maine