Anyway it's not hard to overclock, you simply raise the vcore and the multiplier, testing for stability each time of course. Just read some Phenom II overclocking guides.
If you have a good cooler and you spend time tweaking it, you may be able to get around 4.0GHz. The exact speed will depend on your particular sample. If you aren't going to fiddle with it too much, you should probably end up around 3.8 GHz without too much trouble.
Just make sure you follow a guide and don't do something crazy like setting a ridiculous vcore on your CPU, which could damage it.