Late 2008 unibody MBPs can manage up to 6GB, even when apple officially supports up to 4. There have been discussions on whether they support 8GB considering the EFI update, but the results are mixed - some have no issues, and some have experienced sluggish apps. See here and here.
About the specs, I would suggest to get the exact ones to avoid problems. Normally faster RAM runs on slower machines to the machines speed, so there's nothing to gain from purchasing faster specs. So chances are it will run at 1066, but IMO this is just asking for problems.
Check this out - a few bucks more will get you 6GB (the max tested for late 2008 models) with the exact specs from a very reliable seller in the mac community. If 8GB were supported, I guess OWC would have a kit for it - but for some reason they don’t. 8GB is only supported in 2009 and later models. If money is a big issue, go with 4GB, which is only $70... you'll still see a great improvement from your actual 2GB.
