AE 87 spur
No must. 96T is Kit spur is fine for me
Screw kit
handy but no must
Different springs
Must (associated Springs) : AGREE. Tamiya spring are a NO NO (they rub the shockbodies)
New bearings all around
Kit Bearings are fine
Diff balls
(ABSOLUTE MUST
TI turnbuckles
Not needed really. Kit ones look dull but are fine
Reinforced cup balls
ABSOLUTE MUST. Kit ball cups pop off too easy
Adjustable belt tensioners
Must
Sway bars
Not a MUST, but handy on astro tracks
Diff protective seals
For reducing maintenance : MUST. But : cut your own ! 
Yokomo Shock Shafts
MUST
Strengthened Camber link
Kit one fine for me
Schumacher arial mount
Handy but no must