track pack adds torsen rear diff, different pads that wear faster, and a cooler to what the brembo package has. it also requires 3.73 gears.
brembo is the wheels/tires, front brakes, springs, dampers, strut tower brace, EPAS tuning, ESC tuning, and control arms upgrades over a normal car. can be had in any gear ratio.
2013 Mustang GT Convertible - Very Far from stock
2014 Ford Focus ST - Also far from stock :-) Stage 3 in ricer talk.