Don't connect the speedo to that tacho drive..... Speedo Drive is from the bottom of the gearbox, and as we all know there is no way of preventing oil seeping down the inner cable. The drive spindle has a scroll, later alloy spindle sleeves have an O ring, but the whole design is flawed. A good outer cable with an undamaged outer casing prevents the drips, and that's about the best we can hope for.
Swarfy.