I am keeping the 37's I have now, so I should be able to just barely squeeze under the traffic signals. The 38's are too wide for my taste, despite not having to worry about the air suspension like Tim says. I hope it'll be like Socrates' truck, which I think is one of the coolest on the forum. I think he has the teflon wheels, and mine will be steel.
http://elcova.com/groupee/forums?a=tpc&s=2826088551&f=2606011751&m=302102618