After collecting and checking out informations, here what can help narrow them down

GT : there is a colored red or blue stripe inside the molding . It was standard on the 1987 and 1988 models but became an option for 1989+ ones

Canadian ones are called Cobra GT up to 1992 , 1993 ones are simply GT

There is also a black one found on some cars in the database , i still need to find when it starts ( i think 1989 when the stripe became an option but it still only a theory for now )

LX : The stripe mentionned above was in the option list for the whole run but is smaller
1992-1993 have body colored moldings opposed to black for 1987-1991

both : mirror change on the convertible somewhere during the 1988 MY , coupe/hatch ones remain unchanged
T-top were available only for 1987-1988 , 1989+ couldn't get that option anymore
1989 ones have a Mustang badge on the dashboard for the 25th anniversary
1990 got driver side airbag , canadian ones got DRLs
1991 GT and LX 5.0 got the Pony wheels

will post pics later, on my mom's laptop , running out of gas and for a weird unknown reason its the only one that allows me to create a new topic ( my sister's and my half-laptop can't )

1987-1988 standard, 1989+ optional blue stripe

red one ( that one even has T-top


1989 without the molding stripe and dashboard 25th anniversary badge



LX with stripe ( 5.0 pictured, also available with the 2.3 )

1992-1993 body colored moldings


mirror change
1988 with older mirror

1988 with newer ones


1990 airbag steering wheel
( i don't why the inside badge is there, even found a 1993 with it.. )

1991 Pony wheels



If there is something wrong or to add, feel free to post it

while looking for info about http://www.imcdb.org/vehicle.php?id=832604 , found something highlighted by the 1991 brochure : convertible's top when down is now lower
( 1990's brochure for comparison but is easier to see on that page )

1987-1990

1991-1993

well.. that's kind of embarassing.. no wait, not kind, it is... i forgot to add the 1993 only SVT Cobra . From the exterior it differs on the front by an opening with the Mustang's horse on it, opposed to the closed part with the Ford logo from the GT
Fender receives a Cobra badge instead of GT's 5.0

Rear brings a different spoiler and tail lights that look more like the 1983-1986 ones



They also came in red and black but that color is so beautiful and my favorite by far so i decided to post only in this color...