US-05 is the yeast you want; it's the cleanest dry ale yeast on the market. For the pilsner malt, I'd suggest using maybe 70% rice extract and 30% sorghum extract, with a bit of maltodextrin added. Here's a good thread on the beer: http://www.homebrewtalk.com/f12/sam-...-clone-163003/
, about halfway down the page someone has advice directly from the Sam Adams brewery. It's decoction-mashed, and you could try to replicate that by mixing up the rice syrup with maybe 1/3 of your boil water and just boil that for a bit, then add the rest of the water, do the boil, and add the sorghum. I don't really know if that would simulate it or not, but it seems like it might.