The '90+ cluster is pinned different in back, it won't just plug in to an '89 harness, and vise-versa. Also, it looks a little different; the gauge faces don't come down as far, because the '90+ have the airbag. To get it right you'll need to change your speedo gear at the tranny, or send the gauge out to be recalibrated. I believe Brothers Performance does it for about $40. The gear on the other hand, should only be $10-$20, and it's relatively easy to replace yourself. Call Hanlon Motorsports for the right gear, they will know which one you need and probably have it in stock.