the only difference is the tach in the 96-98 goes to 8000rpm I believe whereas our tachs go to 7000rpm...not much of a difference I can see...if your motor can spin that fast I definetly would not rely on the stock tach.
No advantage really. Unless you get a Cobra one and have a GT more MPH and bigger tach but the stock tach sucks so really only reason to upgrade is if you get a Cobra cluster and want to make it work..