Using a a6000 + focal reducer on a FD 24mm - 35mm will not widen the lens at all. It will increase the f-stop (by how much depending on which flavour focal reducer you by - Metabones, Baveyes, Lens Turbo etc.) and reduce the crop factor (by how much also depending on the manufacturer). For example the FD lens at the low end of the zoom is equivalent to a 36mm in 35mm terms (24mm x 1.5 crop factor). Using a Metabones Speedboster, which reduces the crop by 0.71, means you will land up with a 36mm x 0.71 = 25.56mm lens at the low end of the zoom, and the f-stop by 1 to approx. 2.5