Here are some of the things I have found. They may not be 100% accurate, too many different articles.
GT Plus starts @ $34,995 and includes:
A 14-speaker Harman Kardon sound system with 465 watt amplifier
Hands-free power tailgate
Front Power Seats
Heated steering wheel
Heated Seats
Sunroof
Choice of black or red leather seats (Only Alcantara with the Track Pack though).
Base GT starts at $29,995
Cloth & Leatherette seats
No power tailgate
Manual adjust seats
Base 6 speaker sound system
Track pack: $2,995
Dual-stage-valve adaptive dampers (adjustable from the drivers seat)
Red 4 piston Brembo Brakes
20-inch black Abyss wheels
Alcantara sport seats with red accents (Will lose the leather option above)
Other styling tweaks.(not sure what this is)
Tech Pack: $1,995 (I may have missed a few items on this package)
Adaptive cruise control
Intelligent speed assist
Driver attention monitor
Lane centering
Traffic sign recognition
360 deg camera
Base GT standard-issue active safety is limited to automatic emergency braking, lane-departure warning, and blind spot assist.
The GLH (Goes Like Hell) Package can't be ordered up front like other packages above.
Once the car is delivered, you have to take it to a Direct Connection Power Broker to get added.
This can be done all at once or one thing at a time I believe. It includes The 20" Machined Face and Black Wheels, Lowered Suspension, Performance Exhaust, GLH Stripe Package and possible tuning options..
In order to maintain your factory warranty they have to install everything. Can't do it yourself.
I hope this helps you out.