What is maximum tire you can fit on stock 16" rim. I have 01 F-250 4X4 Lariat. I have seen 285/75/16 up to 305/70/16. How do you update computer and speedometer with different size tire? I don't want to add a leveling kit or jack the truck up any. Thanks for any input. Also any ideas on a good Bull Bar for front bumper.

 

If your stock 16" rim isn't any wider than 7", you don't wan't to go much past 265/75R16, 'cause you'll need to reduce tire pressure to keep it wearing properly. If you reduce pressure, you reduce load capacity. Depending on how wide you're willing to go with wheels, you can get pretty big tires. I know a guy with 44s on a 16" wheel. I don't know how wide the wheel is, maybe 10 or 12"? On your stock, unlifted truck, depending on how wasted your front springs are, you can go as high as 305/75R16s, but you'll probably rub on bumps. My front springs are so bad now that 265/75R16s are about as large as will fit.
As to the guard, I used to have a big Warn one that I don't know if they make any more. Someone told me they still do, but only in black. It was about as basic as you could get, but strong as all hell. It was essentially a winch box made from steel plating ranging from 1/4" to a 1/2" inch in thickness, with steel tubes that reached out and extended around the headlights. It bolted to the frame with some brackets. I'd say they show their worth after an accident when you realize that you'll be replacing you grill guard next weekend instead of your engine. Last sept., after a suberban failed to yield at a traffic light, I T-Boned him at about 35 mph. Were it not for the grill guard, I would have been replacing more than just the grill and the hood. I'd check the Warn website and see what they have.

The Law

 

The 285's are a popular size. I you want hight while keeping the same width try the 255x85x16's. Check this post for speedo recal info: http://forums.ford-diesel.com/ubb/Forum17/HTML/005785.html

 

Does the 285's look good with the 16x7 rim? I am not real worried about load capacity. How about 295's? I really like the stock rims that I have so I am trying to find a way to keep them.

 

I would think that a 285 or 295 would not "look bad", but in addition to reduced load capacity, you'll also have increased wear with the required lower pressure on the 7" wide rims. If I was you, I'd just stick with 265s until I'd gotten wider wheels. In my humble opinion, ya might as well play it safe.
I visited Warn.com today, and the grill guard I had was a variation of the "Combo Kit." Mine just had the steel plate at bottom of the winch box coninue to the top of the box.

The Law

 

I'd be reluctant to run anything larger than 285s on the OEM wheels. Most 285s have a minimum rim width requirement of 7.5". The OEMs are 7", but you can get away with them just fine. The 295s usually require an 8" rim and I'm not comfortable pushing things that far.

Also, if you can't tell alreay ;-), I run 285/75s on my truck. They are load range "E" and I've not yet had any strange wear-patterns. I keep their pressure at the levels stated on the door placard. One thing I do that may help is rotate the tires regularly- every 5,000 miles.