Dale & all
Three decades ago when making it work was the guide. On occasion we would have to use a 70-SS-120 spindle (axle, your choice) to get the correct chainline and assembly providing we were working with French or English BB cups that were best described as the "thin" type. No reverse threading to carry away the dirt.
Shell width did not vary too much but I have had to face a 68mm bracket to 66mm to get a decent face, and then only 320° were in contact with the cup edge. It was my bike 3 decades ago a Bob Jackson. We all felt someone got happy with a vise on the shell, hopefully after it was brazed up.
John Jorgensen
Torrance Ca till 5