speedometers

im wanting to put a full set of AutoMeters in my Isuzu. how will the speedo hook up? i know that on the back of the AM speedo will be set up for GM,Ford or Mopar. i highly doubt that my Isuzu speedo cable will mate with AM gauge.

also, whats the word on GPS powered speedos. that would eliminate the cable all together and be accurate no matter tire size and all that crap.

thanks in advance, looking to get some gauges soon and dont wanna be stuck with something i cant use.