For the 1998-2005 Lexus GS300:
Right Rear, part No. 6913030110
Left Rear, part No. 6914030110
In addition, should you need more information, check out this website: http://www.rockauto.com/catalog/raframecatalog.php?carcode=1418374&parttype=13257&a=Search%2Bfor%2BPOWER%2BSTOP
P.S. "Mine-Right Rear- comes up to like $88.00 total, including shipping."