I'm sure Andre will chime in here, but the recipe he said he was basing his on is here in the Cat's Meow collection. There was a thread about it somewhere here a couple of weeks ago...just can't find it now.
Beer Captured has a Belhaven Wee Heavy clone. I always thought a wee heavy was a little heavier than 90/-, but that's what the book claims it is. If you haven't tried the Belhaven Wee Heavy, to me it's very similiar to the McEwan's.