You do not have to pull the dash. The speedo is held onto the cluster by 5 screws and will come out by itself with some twisting to let the dial clear the opening. Several have had the problem and unless you are really lucky, find the needle and are able to replace it, I believe the end result is speedo usually winds up replaced. The shaft shifts or breaks allowing the cup assy to fall onto the spinning magnet causing internal damage. You can look in Hemmings. I believe there is an instrument repair shop or two that works on King-Seely and possibly can repair it.
Here is one incident and a picture of the cluster.
packardinfo.com/xoops/html/modules/newbb ... ic.php?post_id=31077#forumpost31077 Brandon had a similar problem in his 56 as did another one or two posters.
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