Oh hey, I just belatedly realized something! You're building a fixed-gear, but Dura-Ace 7402 was/is a road crankset. Therefore, the stock bottom bracket spec (112mm) is going to be WRONG for your needs anyway!

I assume you're going to want to run a single chainring on the outer position, since that looks best. That means you'll need a shorter bottom bracket to bring in the chainline. You may have to experiment, but I imagine a 107mm, maybe even 103mm, bottom bracket will be needed.

(If you play with bikes a lot, it's helpful to have a variety of bottom brackets on hand for test-fitting. They could be old and worn-out, but still good for this purpose, so if you needed a reason not to throw away all of your old bottom brackets, here's one. )