Some of the stock 8800GTs are being supplied with the S1 and fans as standard now.
My ramsinks went on once and stayed there, yet they'd be easy enough to remove if I ever wanted to. Some people use thermal epoxy, but that tends to be a little too adhesive.
Mine are attached with only a very thin layer of thermal tape that came pre-applied to the ramsinks. If you just make sure you thoroughly clean the surface with TIM cleaner, followed by surface purifier, this leaves a flawless finish and the ramsinks attach easily and stay affixed securely but not "stuck".
I have the stock cooler and the screws kept safe, should I ever want to sell it as the original product, though it probably has a higher resale value with the new cooler.