Will the ifs handle 36's? or should i run 35's? Mostly be running in mud and some steep hills. What would any of you recomend?  

Is this a 1/2t or 3/4t ?  How much lift do you have?  I have a friend with a 94 1500 Chevy with 6" suspension and 3" body lift and 37" tires and 5.13 gears.  I feel that is pushing it.  I would not exceed 35" tires for a 1/2t and then you should have 4.88 gears, and even with that you may be replacing parts once in a while.  

I read somewhere that you shouldn't put any larger than 35" on the ifs's