Master Cylinder Bellows

you remove that the hole piston will spring out. leave it.
Agreed,
This is what the bellows mounted will look like.

Screenshot_20220417-142537.png

If you have the correct bellows bracket you MIGHT be able to use it and the keeper OR you MIGHT be able to use the bellows bracket in place of the keeper.

Either way if you remove the keeper, keep pressure on the piston so it does not pop out

16502274400147743613406989760811.jpg
Screenshot_20220417-142334.png

I think the OEM MCs had a snap ring to keep the piston in, and the bellows was just bolted on as a dust seal. (I added 2 black dots to show where the bellows bolt holes would be.)
Screenshot_20220417-144213.png