youll find a sticker like this in the boot under the carpet. It tells you the engine code, gearbox, power, and the three letter/number codes are what should be fitted. I've decoded a few here
X2B = National sales program Great Britain\
B0A = Component parts set without country-specific design requirement\
C0Z = Alloy wheels 7.5J x 18\
G0C = 5-speed manual transmission\
H6S = Tires 195/65 R15 V\
J1P = Battery 220 A (44 Ah)\
M51 = 4-cyl. gasoline engine 1.8 L/92 kW 20V with MVEG 2 base engine is T0V/T5Z\
Q1A = Standard front seats\
0JZ = Without determination of weight categoryfor front axle\
1AC = Anti-lock brake system (ABS)\
1G3 = Alloy spare wheel with original equipment tires\
1MR = Leather steering wheel\
5RV = Right exterior mirror: aspherical\
5SJ = Left exterior mirror: convex\
T5Z = 4-cylinder gasoline engine 1.8 L unit 058.B\
0YZ = Without determination of weight categoryfor rear axle\
3S2 = Black roof rails\
4UE = Air bag for driver and front seat passenger\
0G1 = Gearshift lever\
8UB = Radio preparation\
8GD = Alternator 90A\
8RN = Sound package (brand sound)\
1LZ = Front disc brakes, standard ventilation\
3FA = Without roof insert (standard roof)\
C6P = Alloy wheels 8J x 19 front, with 8.5J x 19 rear\
G0K = 6-speed manual transmission\
= code not found :-(\
H6U = Tires 205/55 R16 91W\
J1R = Battery 420 A (82 Ah)\
M5V = 6-cyl. turbo diesel engine 2.5 L/110 kW catalytic converter and EGR, MVEG 2 base engine is T6T\
0JK = Weight category front axle weight range 10\
1AJ = Anti-spin regulation (ABS/ASR/EDL) with electronic differential lock (EDL)\
1G3 = Alloy spare wheel with original equipment tires\
1MR = Leather steering wheel\
T6T = 6-cylinder diesel engine 2.5 L unit 059.A\
0YE = Weight range 5 installation control only, no requirement forecast\
3S0 = Without roof rails/roof load rack\
4VE = Two 3-point seat belts and one static lap belt in third row of seats\
0G1 = Gearshift lever\
8UD = Radio "concert"\
8GL = Alternator 120 A\
8RN = Sound package (brand sound)\
1KD = Disc brakes, rear\
1LB = Disc brakes, front\
3FA = Without roof insert (standard roof)\
1BA = Standard suspension/shock absorption\
}