The state Inspector General’s Office is finalizing a bombshell investigation into the state Thruway Authority that is said to reach the highest levels of the organization, sources say. While the focus is unclear, two sources confirmed the Cuomo administration has already been approaching possible replacements for Thruway Authority Executive Director Thomas Madison. Reps for the inspector general's office, Cuomo and the Thruway Authority had no comment. Billionaire developer Howard Milstein recently resigned as Thruway Authority chairman. One source said Milstein, a big-time donor to Gov. Cuomo, to avoid getting caught up in the controversy once the IG report is released....