The notch LX are the quickest at the track, without all the frills and extra body trim. I think they are around 350#+ heavier than the verts, and only 150#-ish lighter than the hatches.
These are the shipping weights of the Foxes:
LX notchback: 3035
LX hatchback: 3100
LX convertible: 3240
GT hatchback: 3190
GT convertible: 3330
Sourced from allfordmustangs.com:
http://www.allfordmustangs.com/forums/5-0l-talk/141091-what-weight-each-fox-body.html