The V8750 uses the same GPU as the Radeon 4870, so thermal-wise you should be fine with a waterblock for the 4870. However, the layout of the PCB could be different, so better to ask first at Danger Den or Swiftech, or someone else that makes a waterblock for the 4870 if they have something compatible with your card.
-------------------------
Containment BreachDo not meddle in the affairs of archers, for they are subtle and quick to anger.