That RAM was good RAM in the day, as long as your motherboard likes it.
My friend got his to around 950 MHz with cas 4. I don't recommend pushing it too hard as memory can be fragile. The best overclocking RAM I've ever seen was the G.Skill Black PI series which I got from 800 MHz Cas 4 1.8v to 1010 MHZ Cas 4 2.1v which is kind of legendary for DDR2. This was possible because of how low the RAM voltage was at the stock fast speeds. Maybe that will give you an idea of what your looking at, OCZ Reapers came with all different sorts of timings and clocks.
The best thing you can do is slap the timings to cas4 and try a run of SuperPI with the highest memory value. Then increase the clocks 20 MHz at a time and each time try to boot to windows and run SuperPI. Do this until you have a problem then either increase the voltage, I don't recommend going over 2.1v, or lower the clocks by 5 MHz until it is stable if your voltage is maxed. When you've gotten as high as you can go and it is SuperPI stable, then run 8-12 hours of Prime95 blend test. Make sure your case has good cooling before you increase the voltage.