I have a 03 dodge 2500 hemi. Right now i have 33's on it but i was considering putting 35's on it soon. I heard if i get a 2" leveling kit that the 35's would fit. Also right now im getting about 11 mpg on the highway. I was wondering if the 35's would bring it down alot since it has 4.11's in the rear end....i believe?

 

35" tires will impact your MPG's slightly both by rolling resistance and by increasing wind drag slightly. But the effects won't be enough to put much of a dent in your wallet, most likely a fraction of a mpg. You'll probably lose more fuel economy from having a new tread and better grip than the size difference.
Of course, if you don't re-calibrate your speedo, it will appear you will lose more mpgs then you are. Plus it will say you are going slower than you really are.

The gearing, if truly the optional 4.10s, are really good for the 35s, if they are the stock 3.73s, you'll prolly lose a little low end performance...