Well they're like stoner rock/groove rock or something aren't they?
The Big Muff is really you're only choice if so :P
It's THE stoner rock pedal.
Muff, but he uses cranked old Marshalls, Matamps, Orange etc - a lot of bass and mid - thick sound - prob with lots of studio based EQs also
yea, on their last record he used a few old 70s era marshall cranked to max, and i belive an AC30 for some tracks. Gibson LP was his main guitar.

Pedals i can't remember, but it was in the september issue of guitarplayer magazine (the issue with Alex Lifeson on the front). i'll check tommorow.