I'm 280 (recently down from 300!) and 6'1". The Big Agnes Summit Park (http://bigagnes.com/Products/Detail/Bag/SummitPark
)is what I use and love. I also fit into a Montbell SuperStretch but don't like the footbox that much and I haven't seen these bags sold in a while.
Nothing from Western Mountaineering fit me, and I tried several of them. The problem comes when on your back and with your arms to your sides. Unfortunately, the widest part is often down around your elbows. Most bag manufactures only report the width at the shoulders and feet and the bags begin to taper after the shoulders. If it gets too tight around the middle then it compresses the insulation and makes you cold.