Just wanted to share my ordeal with putting in a new sound system in my 1986 GT Convertible. Added Music and seats pictures by poetnprophet - Photobucket
The main issue is that the rear speakers are behind a panel, under the carpet. The mount for them leaves no room for a large speaker.
What I did was cut the panel around the mount, added a 1" spacer, and top mounted it, them glued the carpet, cut the hole, and tucked it back in.
Overall I'm happy with the turn out, even though I messed up on the front door speakers (which, were not there originally....another ordeal). But, I can go a little bigger, so I will eventually, and it'll look much nicer.
Amp is hidden under the trunk compartment for the top, fits nicely.
Someday, I'd like to build a custom fiberglass enclosure for a sub that's ported into the cab, but for now this sounds pretty sweet.
My first Mustang
1986 5.0 GT Convertible: TFTW 170, Comp xe270, Edelbrock Performer, Eibach ProPlus kit, 4 wheel disc, T5z, 3.55.....273hp @5000, 302tq @4500