My truck came with the stock 17 inch wheels, I have 18s for it. They are an inch wider than stock, with an inch more offset so they don't stick out to far. Will a 35x12.50 fit with no lift ?

Yes. It has been done by other members.

My old man has a '11 F-350 with 35x12.50r18 Nitto Trail Grapplers with no lift and doesnt rub

That's what I'm wanting , or the pro comp extreme terrain radials or what ever they are called.

my dad ran 325/65R18 goodrich KO's on aftermarket wheels. I think 18x9s with 5.5 in backset. they did not rub at stock height, but did when he put the leveling kit on it. If you pull the plastic out of the fender well there is a large flange where they joined 2 sheets of metal together that isn't trimmed very close at all. You should be able to grind 1/2 an inch off, probably more, and fix any rubbing issue you might have. Sorry I don't remember the specifics, its been 2.5 years since we did that. You might have to a) drill a hole and use a push stay to keep the plastic far enough back, or b) drill 2 holes and use a zip tie. We did that on a few trucks that the tires rubbed on.

I have the trail grapplers as well and like them alot. Not real loud and handle great and dont have to put it in 4WD alot when im off road. Like Wheels11 said i just took a ziptie and pulled the plastic back about a half inch and no more rubbing.

dad has stock height 35x12.5x20 toyo MT's they are fine no rubbing

Alot of my dads in here...

define "not real loud" ... I'm crazy about not having tire noise