I like Oak for my bows, and most of the pull over 70# (and preferably over 80#). if you're using a good dry stave, then so long as you make sure it's long enough and tiller slowly, you can use the ELB dimensions from Pope's book, but add a few inches in length (6' for instance). Heat treating helps insure that it will reach weight and pull the desired amount. Making sure it's long and bends the full length helps reduce stress. I've used sassafras, red and white oak, and hickory.I've abused oak bows worse than that and they've worked fine at such weights (about 66" long, and narrow) with heat treating.
Though a wide limbed flatbow works very well too. ThimoS posted an 80# red oak board bow on paleoplanet, about man's height, 3" wide tapering in eiffel-tower (sp?) tips.