Is the high resolution screen usable in a Late 08 MBP?

Hi All-

Over the weekend I installed the MacBook Pro 15" Unibody (Late 2008 - Late 2011) LCD Panel High Res Screen (1680x1050 - it was only $30 more, so I figured I may as well), which was originally not available for this model of Mac, and is still a BTO option in the store. The replacement has worked excellently; no more flicker. But, the max resolution I see is 1440x900 in System Preferences. I've restarted a few times, and switched the graphics from the 9400M to the 9600M GT, but still no change.

Does anyone know what I'd need to do to add 1680x1050 resolution to the options?

Thanks in advance for any help.