Well err uh, I was thinking DDR not DDR2.
Anyway, How do I oc ram?
Well, you would do it just as you proposed. You'de raise the core clock from 400 to whatever number you wanted (within reason) but would also have to loosen timimgs (from say 4-4-4-12 to 5-5-5-16) and raise voltage for very little if any gain.
Furthermore, if you recall, I urged you to OC you CPU to 3.6 Ghz to sync your clock speeds at 400, which you did. Now you are proposing to un-sync the RAM, which means that the RAM will be waiting on your CPU for data.
Synced clocks eliminate any bottlenecks from the process. Un-synced clocks will run as fast as the slowest component, so, unless your willing to OC your CPU higher to match your new higher RAM clock you will gain nothing and likely have stability issues as well.
Good luck.