Like fohat.digs said, you will have to drill several holes with a slightly smaller diameter then the screws, in the positions I marked with the white marker, the positions of the former rivets. After that you begin to screw in the screws, obviously after you put everything back together. After everything is screwed together, you put it back into the case and put your keycaps back on, done.
So I need to drill a small hole and then only the screws?
But if i did it wrong will it be a huge problem?
Like the keyboard isn't usable at all
g2136889#msg2136889 date=1460553015]
If you know what you are doing its a pretty easy fix, since I'm located in Germany I wont be able to fix it for you but you can easily do it yourself. You will of cause need replacement parts, so I would suggest getting a beaten up old model M (that preferably doesn't work any more) for near to noting and using it for spare parts (springs). What you do it opening up the case of you SSK (with a 5.5mm nut driver), remove the key-caps and then removing the remaining rivets on the backside of the steel-plate which are holding it together. After you did this it should come apart (can be a bit fiddly, be patient). You can then separate the layers and replace the springs. After you are finished you line up the layers carefully and then replace the rivets with screws. It helps if you mark the former positions of the rivets with a white marker. Your Model M is then "Bolt modded". Put your case back together, put the key-caps back on, done.
Can I just buy new springs from pckeyboard.com?
they seem to be selling new springs too
But is doing the mod hard?
I'm not sure if unicomp uses the exact same style switch as the IBM ones do, I have never owned a umicomp. In any case I would go for the original parts, just in case. But there might be someone who has experience with unicomp parts, I'm not the one. The mod is a little fiddly, especially if you are doing it for the first time. The only really "tricky" part is to replace the rivets with screws, anything else cannot really go wrong. Make sure you keep in mind in which order the layers come together in the end, since you will have to put it back together again. There was a Video on YouTube on how to Bolt mod a model M, but it was deleted recently.
I quickly took some photos for you, which show you all the different parts when you take a Model M apart, and also show you how to put it back together, how to mark the positions for the screws and how to line up the parts again, as well the putting the board back together, I hope that gives you a idea. Sorry for the rather crude image quality, I took them quickly.
Warning: many pictures!1: The parts, or layers:

2: The former position of the rivets and where I marked them with a white marker:

3: A closer look at the markings:

4: lining the layers up again 1:

5: Lining the layers up again 2:

6: A closer look at the layers 1:

7: A closer look 2:

8: Having all lined up 1:

9: Having all lined up 2:

10: putting it back into the case (that one didn't came out well):

11: All put together:

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Woah, really thank you for all of the picture

How much screw in needed approximately?
and what size of screw?