Giant Bomb and Steam

I'm planning a bit of a mashup between Steam and Giant Bomb, and need to figure out a way to match Steam and Giant Bomb games. In effect, I need to create a relationship between the GB game ID, and Steam's AppID.  
 
Has anyone attempted this, or is anyone aware of any info floating about to help me along? 
 
How would YOU do it? 
 
Thanks!

Sorry to resurrect a 5 year old post, but @beforeseven is asking the exact same question I would ask. We would love to do a crosswalk of GB game IDs with Steam's AppID for Lifebar, so if anyone has done anything similar, it would save us boatloads of time.

Thanks in advance.