I am confused as to what you want to do. You can link two identical graphics cards together, this technology is called crossfire for ATI cards and SLI for Nvidia cards.
For e.g, I have got 2 separate ATI 6950 that are linked together using a crossfire bridge.
You have to have a motherboard that supports crossfire.
Your motherboard would need to have two PCI-E slots in which the cards would sit.
Please explain a bit further and I may be able to help a bit more.