If it's an X58 motherboard, it should support Crossfire and SLI, all X58 boards should as Nvidia haven't released a new nForce for x58.
Gigabyte GA-EX58-UD3R, Intel X58 Express, S1366, PCI-E 2.0x16, DDR3 1333, SATA 3Gb/s, SATA RAID, ATX - Scan.co.uk
Look at the technical specs. It says it is SLI capable.
Saying that, to enable SLI, just put both cards in with the bridge on, install the latest Nvidia drivers. Once installed go to the Nvidia control panel, go to SLI and Physx settings and enable SLI.