Just used standard Rover gauge that came with a mk3 Rover. Electric speedo. Sensor wire was included in the Marlin loom so just used it. Only needed a switch positive and earth on the sensor end and worked ok.
Original speedo (early Rovers) used cable speedo drives. Not electronic.
Have been thinking about other istruments. I did like these, but is a bit pricey!
http://shop.aim-tec.co.uk/mxl-strada...aphics-4-p.asp