I normally wear a street size 10.5, sometimes wide width, depending on the maker. I have a wide forefoot and a regular heel, so I've had to order and send back lots of boots to get the right sizing. Length has never been a problem, it's width. I had a pair of Aku Spider boots, size 11.5, and the width was still to slim for my foot. I changed out footbeds, moved the tongue all around, changed lacing systems and sock thicknesses, this particular Aku was just too narrow for my foot. Put it this way, Keen shoes fit great, but they're not into mountain boots, so that's that. You should be going AT LEAST a half size up, anyway, to account for foot swelling and good socks. I've had to go a full size up on all my boots, change the footbeds out, the right thickness sock, and voila, working, comfortable boots for the long haul. One thing: Aku makes splendid footwear, the Spiders were absolutely blast-proof, I'd still be happily using them if only they'd have been wide enough. Good luck!
The size 8 will be too snug. Go for the size 9, they'll be better.
These shoes fit slightly big as far as length goes, so purchasing your normal street size will probably put you in the right range, and make sure that you have some extra room to prevent toe bang and such. Make sure to review our fit guarantee, if the size that you order doesn't fit, we'll get you the right size if we have it in stock (US purchases only).