So you're a pretty big dude. In my mind, your minimum shoulder girth in a bag would be 63", and you might be happier with a 64"+ shoulder girth.
For an example, I'm 5'10"/155lbs/40-41"jacket... my preferred shoulder girth is 62", though I've used as small as 58".
I use a WM Versalite which is what I'd refer to a "30-06" bag. It can cover most bases. It's rated at 10*F, but I do use it in the highcountry on summer backpacks. It's an ideal fall elk hunting bag.
You're going to need a "tall" sized bag (up to 6'6"). Good news is as bags get longer they are typically made a bit wider.
Versalite in size long has a 63" shoulder:
http://www.westernmountaineering.co...at=ExtremeLite%20Series&ContentId=20Ditto Antelope:
http://www.westernmountaineering.co...cat=Microfiber%20Series&ContentId=37Badger may be your huckleberry with a 67" shoulder and 15* rating:
http://www.westernmountaineering.co...cat=Microfiber%20Series&ContentId=34The Alpenlite has a nice 65" shoulder girth in the long size... a really great bag. Both my wife and her girlfriend both have this bag, and even though both are pretty svelt, appreciate the extra room:
http://www.westernmountaineering.co...at=ExtremeLite%20Series&ContentId=28Push to shove, I'd recommend the Badger or Alpenlite for you... if you can find a local retailer and try them out, so much the better.
Hope any of that helps.