Well, my brother took the car to a wheel/tire shop. They ended up putting 5mm spacers on the front, and the rears fit without an issue.
(BTW, this is the stock painted 19" wheels from the 1LS/2LS to a 2012 Camaro SS.)
For some reason, the 19" tires are a bit cheaper to get than the 20s, and didn't want to get into the swapping tires game for winter, as swapping tires on rims are much cheaper and easier to do at home. Not to mention easier rotations.
Thanks, and happy winter driving!