This is what the schematic in my manual says. The book is for a 1987 Firebird, should be the same. May be easier if you did it this way
http://www.crutchfield.com/App/Produ...677&c=3&tp=736
C1
E - Pink - Antenna
f - yellow - power
G - Black - Ground
M - Gray - radio back light
C2
A - Lt. Green - RH Front speaker
B - Tan - Lh Front
C - Dk. Green - Rh Front speaker
D - Gray - Lh Front
C3
H - Brown - Lh Rear
J - Dk. Blue - Rh Rear
K - Yellow - Lh Rear
L - Lt. Blue - Rh Rear
C4
A - Orange - Clock Power
B - Brown - Display Dim Signal