Originally Posted by
the sci guy
I'm definitely overthinking this, so if you have a minute can you please read and talk me down off the ledge? Cool, thanks.
No worries about overthinking. I do it all the time. My recommendation is to just initially use your existing bottom bracket. The two reasons for this recommendation are 1) since it was sized for a triple, with the center ring the optimal one for chain line, it may be right on the money for a single (which can be considered a triple with out the inner and outer rings, and 2) it's always easier for me to figure out spindle lengths by mounting a new crank on a bottom bracket, measure the chain line, and then use the difference between actual and target to determine the spindle length of a new bottom bracket (if necessary). Different cranks will fit differently on the same tapered spindle but it won't be much.
I like the looks of the Sugino crank, but if you want to consider used cranks look for Shimano 600 cranks on ebay. They are nice quality 130 BCD cranks that I've used to set up a couple of 1x bikes. You'll probably want a narrow-wide chain ring to avoid chain drop - I like the WolfTooth rings.
I would not trust the bottom bracket recommendations for the Sugino. It may be that they are assuming a certain cog configuration like a track hub that has a 120mm OCD. Best to try the crank on your existing spindle and go from there. I know you need to replace it, but remember that it's for testing.
What size ring will you be using? I wouldn't think that any ring smaller than 48t would hit the chain stay, but again using your current BB will provide insight. And yes, you will need a 3/32" chain.
Good luck