Alright, so you'll put the first card in the first slot, and the second in the third slot I'm guessing, so you'll need an SLI cabe that is 3 slot, not 3 way SLI, but 2 way, 3 slot SLI cable.
http://www.evga.com/forums/tm.aspx?&m=1999556 You should be fine, look at the first picture, there's a 2 way sli bridge connecting a card on the first and third slot, just like you'd do.