they are easy to wire up,theres loads of spare wires though.the shape of them will mean loads of cutting of the plastic surround as vauxhall clocks are wide at the bottom and narrow at the top,other way round on fords.i think some mk4 xr3i's and rs's with the fuel gauge had a transducer on the gearbox that the speedo cable connected to.that gave a pulse for the computer to innacurately work out how much fuel was left.im sure i have seen that used when fitting 1 in an escort.not much use for a sierra.the 4x4 has a similar thing on the front left casing where the driveshaft comes out iirc.looks dated now though.