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.The Cherylkee....
2003 Range Rover HSE, 4.4 Quad Cam.
1998 Range Rover 4.6 HSE
2000 4.7 4WD WJ with a rebuilt motor.
4.3/700r4/new frame buildup (YJ)....
Years to gain the hands on experience, and offer it freely.
Minutes to gain the knowledge from the internet, and quote it just as freely.