Of course. Many OEM vendors make both GDDR3 and GDDR5 versions of graphics cards. However, you ALWAYS want the GDDR5 version if possible, since the GDDR3 version will be slower.
But regardless of the type of VRAM used, it will work in any PCIe x16 slot. The version of the slot (2.0, 3.0) doesn't matter. PCIe slots are backwards and forwards compatible.