Further to Jim's answer, to save having to chop a TD5 harness up, you can make a plug for the back of the speedo from 2 radio plugs glued end to end and then cut down. As Jim says the transducer plug is the NAS type which you can buy singly on Ebay
My conversion was christened on our Pyrenees trip and it was nice not to have to average the speed from the flickering needle.
Another thing I noticed is that the speedo was spot on to the gps with 255/85r16 and a green speedo drive.
Ralph, A search should show some companies that will zero or change mileages on electronic speedos.
Any progress Jim, on the lights, I'm chomping at the bit here
Mo