I'm with Calder, on the bread-vs-malt comparison...not a fan of rye bread, but put rye malt in a lot of beers.
Without seeing your recipe, I might split the two- 1/2 lb of wheat (for head retention) and 1 lb of rye (color and flavor), or something along those lines. A big stout can handle both the body/mouthfeel that the wheat will bring, and the spice of the rye, hard to go wrong with either.