Are you thinking of replacing the existing Guild Bigsby with a Bigsby B70? I don't know if it's an exact retrofit, but apart from the cosmetics, you'd be getting the exact same thing, so I don't really get the "why"?
I am pretty sure that Guildsby parts and Bigsby parts are not interchangeable due to slight sizing differences Caused by NS guitars being Korean made. However, I don’t know if that applies to footprints...