BTO is your best option, but vary the spec. slightly to store stocked models or they'll send you UK store stock even though it says "ships in 3 days".
You can go to a store (or phone them) and ask them if you can check the serial numbers of their stock here.
The fourth and fifth characters of the serial number indicate the production week, e.g. mine starts C02F9 which is week 9, C02F8 is week 8, not sure how week 10+ is defined. Week 19 onwards certainly seem to be 6/6 but it may not be as simple as that. Good luck!
Oh, you'll get blank stares from any "Genius" if you mention why you want a recent build. Rather than get drawn into awkward conversation it's better just to say something like: you read somewhere that SSDs work better on recent builds.