Here is some information related to repairing Mac Pro's
2006 to 2007 - RV630 256 Mb Radeon HD2600Video Card works. The part number is 630-8924
2008 - We found that the Genuine Apple nVidia 8800GT 512MB Video Card for the Mac Pro Part Number 630-9368 works fine. The 630-8924 works in our 2006 / 2007 but not in our test 2008 Mac Pro.