does the gauge manufacturer not make a harness for it?
electronic speedo's work off a pulse system i think, and you would need to match the pulses to the gauge.
otherwise the cheapest option would be to trace the wiring for an electronic speedo in the shop manual.....basically it needs a power feed, then the wire to the gauge. there will be wire(s) to the ecm also, but you will prob b ok to bypass these, as they would mainly be used for the cruise, auto tranny etc.
1998 XJ on 37's.JK Rubi axles with chromo shafts and ctm's, 4:1 transfer case, etc etc etc.
2003 Range Rover HSE, 4.4 Quad Cam.
1998 Range Rover with a 6.0 LSx
1994 YJ, 4.3/700R4/OME SOA, etc
Western Star 4900EX 4 axle.
4.3/700r4/new frame buildup (YJ)....