I am assuming the cone screws you are talking about are the ones holding the ignition lock assembly onto the column? You don't actually need to unscrew these to take the column out.
They are like that as an anti-theft device, i.e. make it hard to disable the steering lock.
I have always been able to get them out in the past with a hammer and screwdriver. Basically you belt a slot into the top of them. As you strike the hammer onto the screwdriver head put a bit of rotational torque on the screwdriver to unscrew the bolt. This can take a few blows but always works for me.
I wouldnt go using my favourite screwdriver for the job though!