If you care to know your speed, just buy a new speedo.
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2444541258
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2444154040
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2445594577
As long as you keep a record of your actual mileage, you'll be legal. That last link sounds like a bargain if you can take the front plastic from your current gauge cluster to use on the new one.