You need to call the store you are going to and ask.
They do have more than the standard configuration in the store, that is a common myth that is perpetuated here on MR.
They always have the standard config... but the individual stores can order stock of BTO type configurations that sell well in their area.
As proof. I am typing this on my 2010 MBP with 2.66ghz i7 with Anti Glare. Which was a "BTO" option, not "Standard". I stopped in the store to play around and one of the employees asked me what I was interested him. I told him I was just trying one out and would have to order online because I wanted the 2.66ghz with AG. He said "hold on one min" he came back about 5 mins later and told me he had it in stock. I walked out 15 mins later with it.
3 Days ago, I went in to the Apple store and walked out with a 11" 128GB 1.6ghz 4GB RAM Macbook Air... which is also a "Buy to Order" model, they had it in stock.