If the heatsink will fit a socket 370, yes you can use it. Line up the HS on the socket and be sure the step on the socket fits the lip on the HS and that the cpu core is in the middle of the HS. If these all line up, it shouldn't be a problem.
Whoa, I didn't read it carefully. If you are overclocking it to 850, you may need something bigger. Try it and see first and if you can't get where you want to go, buy a better cooling rig.