I have the '02 LS 430 and, as you know, the '02 has 16in. wheels, whereas the '03 comes std. w/ 17inchers. That in itself will make a difference. Officially, Lexus says that you can go from the 16 to 17 by changing the tires as follows:
The 17" wheels and tires are an option for your vehicle. The information for the 17" wheels are as follows:
7.5" Width
JJ Flange Type
45 mm Offset
114 mm Bolt Pattern
M12 x 1.5 Wheel Fastener Size
Recommended tire profile size is 55.
The quality of the ride for the 17" wheels will vary from driver to driver. We recommend that you test drive a like vehicle with the 17" wheels before considering upgrading.