I suppose that you could get a gear to re-calibrate your speedo if they make one with twice as many teeth as the one you have. Otherwise just get a 87-89 140mph speedo. You can get the whole cluster if you like or you could just get the speedo and swap it in. The 90-93 have different cuts at the bottom of the gauges and I actually think they will work too but the 87-89 won't work in the 90-93. I'd have to check but I've done a bit of swapping in the past.