You need the mounting brackets for a 13 Base car to mount the aftermarket speakers. I pulled this quote from another thread
Right off my invoice
4R3Z18B947AA body hardware, instrument panel, sound system, door speaker spacer COUPE Right 1 $0.00 $11.14 $11.14 4R3Z18B947BA body hardware, instrument panel, sound system, door speaker spacer COUPE Left 1 $0.00 $11.14 $11.14
13 GT base, 3.55, Sterling Grey, MGW shifter, BMR LCA's, GT500 AB, silver RTR's, 275/40/19 Michelin pilot super sports, more stereo equipment than I will admit to, more parts to come.