Al - my car came out of Washington state, so it's not that one.
I've only got like 3/4" (if that
) sidewall clearance on my tubs and fenders and they don't rub. I run a wishbone so it can't move around too much. I agree with Randy, if this is a street car I'd allow more for going over the rolls and bumps you'll encounter out there.
Diameter-wise I wish I had a bigger tub. I've got less than 2 inches between the tire and the front of the tub. It polishes the tub now and then
- not bad, but it hits. I've only got 29" tires - your 33's will grow a bit more.