Good question. As far as I know, you should malt the grain to suit what is called for in the recipe. Whether it's a Porter beer, or a Bourbon whiskey, they will have a basic recipe calling for a certain kind of malted grain. There is no difference in how you malt the grain to get the correct malt from it. Beer and Whiskey are both mashed and fermented similarly (Except that whiskey might be made to a higher OG and fermented a little warmer, and with a high alcohol strain of yeast.)
The malts should be the same between the two processes. I think they usually use a fairly basic base malt, but I'd be interested in tasting the difference between a basic 2-row whiskey, and one made with all dark Munich.
