I am putting a new Sugino XD500 triple crank and new cartridge-type BB on a '83 Miyata 610. The old "cup and cone" BB spindle I removed seems long----124 mm (excluding the threaded ends). I think it was original, but can't be sure. The bike was a CL find, and I rode it very little before stripping it down.

Question: What length BB spindle seems right in this case? What will give me the optimal chain line? I am putting a new 7-speed Shimano freewheel on the original hub. The rear DO spacing is 126 mm.

THANKS!