Google isn't indexing a client's UBB6.2 board. Any suggestions on mods that can get the bot finding the entries and getting some search engine juice?

Well, it's probably just due to standard bottlenecks with scripts and using ? and ='s; which is why later versions started having SE compatibility modes which replace the strings... So, I doubt you'll want to hear it, but a simple upgrade brings you the feature you want and security fixes you'll likely definitely want.