If you have the Sapphire HD 5750 1Gb GDDR5 it will work if you edit the plists for the AMDRadeonAccelerator.kext and the ATIController.kext.
Enter the ID for this card 0x68be1002 in both plists. The GPU on this videocard is Juniper. Edit under where it say Juniper in the AMDRadeonAccelerator.kext
To get the displayport to work in order to get three displays you need an active dipslayport to dvi adapter.
In Extra you need DSDT.aml and org.chameleon.Boot.plist SMBios.plist for Mac Pro mid 2010.
In Extra/Extensions only fakesmc.kext.
For network use the RealtekKRTL81xx-0_0_90.pkg
To speed up the boot time use AppleAHCIPort.kext and IOAHCIFamily.kext from Lion
I attached the files
Use the latest Chameleon and kextutility