In starting to work on my brakes on this big ol truck I ran into an issue right off. The nut on top of the mc has been stripped pretty bad and its impossible to get a wrench or socket on from the top. The floorboard hole is too small to get anything thru onto the nut. From underneath I can't get anything on it either suffiecent to get enough torque to bust it loose. Is my only option to remove a cable that's in my way, or either remove the whole mc itself ? It doesnt look easy whichever path I take

Thanks