Windsurfer brand mast clip size/type

Question
I recently acquired an old mid 80s windsurfer brand windsurfer.  It is complete except for the hinge thingy that attaches the mast to the board.  I have looked online for the attachment and noticed there are many types.  I have attached a link to a few pics of the slot/lock on the board.  If you could please point me to the type/size of the thing that I need to connect the two.  
http://users.rcn.com/spikemcl/DKLM171.JPG
http://users.rcn.com/spikemcl/DKLM172.JPG
http://users.rcn.com/spikemcl/DKLM174.JPG
thanks!

Answer
Hey Mike,

I must say that you got lucky with the type of mast/board connection. A couple of years older and you would have had trouble finding the part. As it is, you should be able to use any modern type mast base. I will include some links for you to check out and then all you will need to do is shop around for the one you want at the price you can afford.

The modern base will have a threaded stud sticking out the bottom of the universal joint (rubber hourlass). This stud should thread directly into the hole in the middle of the rectangular plastic part on your mast track. If you press the pedal at the back of the mast track you will see that the round shaft rotates to expose a slot. With the pedal down, thread the mast base into the part until it is tight. Then slide the track until it lines up with one of the slots and release the pedal. The stud should slip into the slot to lock the mast base into position. This was one of the earliest types of movable mast tracks made. Very simple but functional. You only have about 6 choices of mast locations but it made the sail/rig much more versatile being able to move it. Forward will be for light winds and going upwind, middle area for moderate winds or offwind speed, and back will be for higher winds and more speed.

Bases are the basic part of the mast/board connection. They consist of the u-joint, stud into the board, and the mast foot/base. The base/foot will have two pins. These will lock in an extension to the base. As for length of extension to look for, you can probably get by with a short to medium length. You should be able to figure out what I mean when you look at the pictures in the links.

Shop at any of the links or for a few less $'s, check out ebay, craigslist, or your local shop for used gear.

http://www.chinooksailing.com/products/  Check out the single bolt bases and US cup extensions. You could go with the euro pin type but US is more popular and universal.

http://www.bigwinds.com/wind/category/5  Extensions can be found by clicking on the link to the left

http://www.windance.com/  Check out new bases/extensions under windsurfing and used  ones under used gear. Their rating system is right on or half a point low. Great place to buy gear from.

http://www.oceanairsports.com/cat/Windsurfing5.cfm  Another place for new stuff and misc parts for a variety of boards.

Hope this helps.
Keep on sailing,
Windlover