I5-760 3.6 Ghz

The newer sandy bridge will take this on a performance per clock per core, from what I can determine from existing benchmearks. The I5 750/760 does scale pretty well with overclocking, though it doesn't directly translate into 1.28x as in your proposed question, it'll be close, but not direct math. Clock cycles are "lost" for performance purposes from various overheads as clock speeds increase.
Obviously those lost cycles are addressed somewhat in the new architecture in the sandy bridge, since the amount of work per clock actually increased.