I have purchased a truvativ bottom bracket adapter form my early 70's schwinn continental. I have also decided that I would like to purchase a used vintage shimano 600 crankset. They seem to be easy to come by online. I have been doing some research online about bottom bracket sizing, and I want to make sure I purchase the right parts. Does anyone know what size bottom bracket axle I would need to keep my chain in line after the conversion? I know I need to purchase a 600 series BB if I am using that series crankset. I would like to go with sealed bearings. I'm just concerned about keeping thing symmetrical on my vintage bike. Please any advice would be great.