Stock would have been the Shimano FC-6206 (aka N600), and this shows the spindle length as 121.5mm:
https://velobase.com/ViewComponent.a...115&AbsPos=352
That said, you may or may not need the same spindle with the mix-and-match Sugino/Shimano set you have now. Since you need to pull the bottom bracket anyway, you'll just need to measure and have a little trial and error.