I am building a new bike because my old one got hit by a car with me on it. And hopefully I'll have some money to play with. I am considering buying a basso coral frame and all ultegra components. My question is does the bottom bracket measurement of either 68 or 70 deal with the frame or the crankset. Or, more bluntly, do I need the BB with Italian sizing of 70 to fit my frame or does that number correspond to something else. Thanks.