Mast foot is relatively newer generation of gear compared to board mast track and is not compatible.
A windsurfing shop in Perth
http://www.surfsailaustralia.com.au/listProduct/Windsurfing/Mast+Baseshas various mast bases but not sure if any of them would fit your board - best to ask them.
In relation to board; having started myself 18 months ago on an "old school board" like the one you have, and then got more serious and purchased newer gear, the answer I would give you would be -"it depends on if you are serious about learning and how much your time is worth?"
You could, and people have in the past, learned to sail on such equipment, but newer gear is so much more user friendly and easier to learn on. For example, the board I purchased soon after starting was 76cm wide, and let me tell you, I was instantly better as soon as I stood on that board than I was before; just more stable.
Windsurfing perth has a couple of JP Funsters for sale a 130 Litre, and 205 Lt.
www.windsurfingperth.com.au/en/gear/used-gear/used-boardsThat mast base would fit on them as well. Or you could keep your eye on secondhand market for something to come up.
So yeah, if you can afford to get yourself a floaty, wide board, I would highly recomend saving your time, effort, and money, rather than searching for parts for the old board. There are plenty of posts similar to yours regarding what type of gear to get to start on. Generally speaking you want something around 60 litres more than your body weight at least as a learner board. So if you are 90 Kg, then a 150lt board or more would be good. Learner boards also hold their value so you will be able to get a good return on it should you choose to sell it down the track.
If on the other hand you're not sure whether you want to take up windsurfing yet then spending $50-$100 on parts might be alright to start with.