Hey
Im in the same boat you are, I have a vintage shimano rd crank, and have yet to get the BB.
Mine is an EXAGE sport, with the original intended bb being a 113mm for double set up.
If you have the late 80's DA crank (7400) I used to race on this one back in the day, and it used a 112mm bb, so in your case, with a high end crank that already has a narrow Q factor, Id get a shimano 115mm BB, and run the ring on the INSIDE, because originally , with the stock BB, you'd get an inner ring chainline of about 41mm (too close), so the next size is 115mm.
Good luck, and tighten down cranks pretty hard, you can safely go up to 50 Nm in torque.clean taper and spindle before installing with cloth, no need to degrease so its a bone dry taper though, just a faint bit of skin oil should be fine, but dont grease spindle like its an Octalink.
Jack