You can't replace plastic rivets by bolts ! These model M have been riveted using a factory machine to ensure iso pressure on all the the metal-films-plastic sandwich. I tried this and killed mine for ever (my best score was 2 keys not working but never came to 100%).
It's technically impossible to screw all 50+ bolts with same pressure, and if you can't, some keys won't operate, or worst : your keys layout will look like hills and valleys^^ The metal back pane is a tank, not the black plastic pane holding the springs in place.
However, if you try this, prepare to spend more than 30 hours (more than 50 holes to do), you MUST have perfect tools, and prepare to end up with a dead model M...
What I would do If I had to repair one again :
1. Ensure all electric internal connectors are clean and/or clean them with 90% alcohol and test again
2. if still bugging = dirt, water or rust came on contact films in the "do not dismount" part making short circuits
3. buy several 90% alcohol bottles, enough to make this part take a long bath (2 to 6 hours) shaking it every hour (use a mask or get drunk^^)
4. let it dry in a warm&dry place, vertically (caps lock key bottom or top) for several days
5. optional : you can lubricate BS mechanic with appropriate silicone spray (this is not conductive and anyway there is a silicone layer under the B.S.)
6. No need to assembly all yet, just connect all, put some key caps and test, if ok put all keys and test each new key, if still bugging somewhere, go back to 3...
This takes time but not your time and at least you're not taking risks in damaging the heart of this KB.
Maybe some have succeeded with bolts, but I would really love to know if the bath alternative works (it was too late for me to try it).
Good Luck, I know what it is to loose a model M, mine was an AZERTY (1995 IBM UK), been seeking for one for almost 6 months with no result...
This is the main weakness of this KB : this not maintainable part should have been waterproof or using clips instead of rivets...
(or better : following what's described in IBM's patent^^)
!!!! other important point : printed circuit on films is made of conductive paint, never use acetone to clean these films, this will remove the paint ! Alcohol or soap water if fine to clean these if you choose to disassembly this main part.
