They're compatible. Be aware that the stock thermal pad on a retail AMD heatsink isn't meant to be re-used, so make sure you have some good-quality thermal compound on hand.
The 6035 is a very good heatsink, could it be the older variant with the weak clip, and isn't overcoming the cornerpads on the CPU and making good core contact (the older clip has a semi-circular pressure point instead of two 45-degree anglebends)? Is it on in the right direction (stepped edges over the cambox and lever of the CPU socket)? Thermal compound? What kind of fan?