2005 f-350 super-duty running gear

http://miata.net/garage/tirecalcold.html

You might also want to look at a power programmer. They usually have a function to adjust your transmission for larger/smaller tires.

pullin gear not highway

with 36' tires the biggest gears i would go with are the 4.56s, they are a little big, personally though, unless you plan on doing some serious 4x4ing i would leave the stock 3.73s in there or maybe go with 4.11 gears because you will get better fuel mileage, the only thing the gears are good for is giving you better leverage to turn those big wheels when your doing serous 4x4ing, and most of the time all you need is 4x4 low, so make sure you get the gear thats right for you. Give any 4x4 shop a call they will explain what i mean.