I would just get a crank with a spindle that you know works for that crank, and try installing it with balls, and see how the fit works. I did this on my Peugeot UO-8. I had a 6207 series Shimano 600 crank with its original BB axle and bearing set, and I decided to see how it fits in the French cups of my Peug. As luck would have it, everything has good clearance and it shifts well, so I am good to go, without modifying the threads of my old frame. If that combo doesn't work, unfortunately there'll be a need to decide in which direction a change needs to be made.

I think the 3rd or 4th editions of Sutherland's discussed matching crank/axle/frame to each other, and would at least show you how to measure and spec the spindles that do work (the old Raleigh) and that might not.