They both have a CPU size of 37.5mm x 37.5mm but the screw placement is slightly wider on 1155 mother boards. LGA 775 is 72mm x 72mm and LGA 1155(and 1156) are 75mm x 75mm. Meaning that thought the plate will fit, unless the mounting screws can be moved out, it wont fit the motherboard.
+1 to SirMonkey, the ACFreezer 7 Pro is crap compared to even newer cheap models. You would get better overclocks (if there to be gotten of course) on a more modern capable new HS, not to mention one with a 120mm or larger quieter fan.