If it is with the digitizer, there are 2 extra right hand 'brackets' for screws at the bottom of the 3GS screen assembly, so this would be 3G only.
I only post as I recently needed the exact same assembly for my wife's 3G (I had the phone for 15 months, not a scratch, and the screen broke within 2 days of it knocking about in the bottom of her handbag!), and initially got sent the wrong one.