Measure the chainline you get with the chainring on the inside, take the difference between that and what you measured on the hub, double it, add that to 103. This is the size bottom bracket you'd need. For instance, if you measure 37mm on the inside, you'd need ((40-37) * 2 + 103) = 109.

I'm guessing 109 is what you'll end up with as the XD's are supposed to give a 42mm chainline with the chainriung on the outside, and there's typically a 5mm difference between inside and outside.

Measure twice, buy once.