This is a tough question. The best possible draw weight would be the draw weight you could shoot the best or close to it. With the equipment we have today a 60# bow could and will take an Elk cleanly in the right hands with the right shot. That given though the shooters skill will come into play more then the draw weight. The bow I shoot has a kinetic energy valve of around 90fps with the correct arrow weight. That is plenty for Elk and almost any North American animal. A friend of mine just came back from Africa shooting an 80# version of the same bow. He shoot a Kudu from a ground blind at 27 yards and the arrow passed through just behind the shoulderblade. But he was shooting a 750 gr arrow too. So that said it is way more then what you'd need for Elk, but should put you on the right track in figuring the best draw weight for your needs. Shoot the most weight you can accurately for Elk and it will more then be ampeal from any deer you run into.

I shoot 60# lbs on whitetail and have pass through with my fixed blades every time. Elk i would think it would be a better idea to go with a heavier weight just because theres a hell of a lot more there than with a whitetail.

I say 60 lbs. for whitetail and heavier weight for elk like Crazyhunter said

The highest weight you can draw and shoot comfortably and accurately,there is no such thing as over kill with a bow with a good shot,just how far do you want thar arrow to stick in the ground after that pass through...I shoot 64 lbs because I can practice at that weight all day...