There was a guy on WeightWeenies forum that was building custom BB30 cranks that fit in BSA bottom brackets. He is not doing it any more. It is not simply a matter of replacing the bearings, which can be easily sourced, you also need to replace the actual crank spindle in order to get the chain line correct. Unfortunately Cannondale does not make the correct length spindle any more and I am not sure if he has gotten permission from Cannondale to build his own.
A long story just to tell you to sell the Cannondale crank and buy one that fits your new Ridley.
A forum community dedicated to Road Bike owners and enthusiasts. Come join the discussion about bike parts, components, deals, performance, modifications, classifieds, troubleshooting, maintenance, and more!