All Classified forums require a Site Supporter subscription. It is only $25 per year and you can buy and sell whatever you like on the forum. To become a Site Supporter, go to Your Profile and select "Paid Subscriptions."
I have replaced the speedometer cable from the back of the speedo gauge to the trans tail housing only to find out it was actually the speedometer itself. Now the only thing left to do is change the drive and driven gears in the trans tail and it will all be new. Nothing very hard. The cable was the cheapest to replace.
If all you did was pull the cluster and replace it, are you sure it wasn't reading lower before?