That's good thinking.

The BB makes a nasty sound even on the bike stand when the rear wheel is just turning over the chainset (I'm running it fixed), so I've just assuming it's knackered. From the reviews I've seen it won't be long before it really is knackered, so some preparation for the event can't hurt

The Shimano 105 BB is said to be 43.5mm, whereas the Sugino BB is 42mm. I suppose the extra 1.5mm will mess up the chain line.