When in doubt go to the manufacturer's website as all the others are subject to human error. All show both belts on the AC and WP

V8 4.6L
2002-2003

Serpentine - AC.............................. 5K1023
Serpentine - WP, ALT.................... 7K1623

Now on their parts finder it says
V8 4.6L
2002-2003
5K1030 which is 1030MM in length

Penske Parts
11287507626 RIBBED V-BELT - 5K X 1023
11287507626 was superseded by 11287636374.
11287636374 RIBBED V-BELT - PK5X1023

Euro best price on AC belt Accessory Drive Belt (5K 1023) (A/C)
2002 BMW X5 4.6is (E53) 4.6L 8 Cyl (32 Valve) Engine Parts - Free Shipping

Serpentine Belt (5K 1030) - Continental 5K1030
SAAB Serpentine Belt (5K 1030) 55556404 - Continental 5K1030 - Free Shipping

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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green