I have a 1980 Schwinn Super Le Tour that came with the usual Sugino bottom bracket assembly and Super Maxy crank set typical of most of these bike models.

I have a Shimano 600 crank set that I want to use, but it sits too wide on the Sugino spindle, so I want to swap out the bottom bracket and spindle for the appropriate Shimano 600 version.

So, my question is: What model am I looking for here? Can I just swap out the spindle, or do I need the whole BB set?

I'm new to this level of bike repair/modification, so a bit confused as to the threads that are used for these bikes (Italian, English, ??).