I'm building up a 72 P-15 Paramount frame. I was planing on using a 1st generation Dura Ace crankset (double) that I acquired. The dimensions for the bottom bracket I believe should be 68 mm by 112 mm for the spindle length and english threads. I've seen Dura Ace 7400 BB for sale with these dimensions, will they work with the first generation Dura Ace? How does the Dura ace # sysytem work (year) ? Did the first ones have a #? I tried some cups from old japanese BB and they threaded on fine but the cup with the two flat sides did not completely thread on at the very end where the threads ended on the cup but continue on the frame (at least that looked like the case). Any thoughts?