I have a 79 supercab F-250 4X4 that I am about to put leveling springs on the front. My question is: with a 4inch backspacing wheel, how much flare do I need to cover a 33/12.5/16 tire? I want the tires to "fit" the fenders without being swallowed by the fenders. Thanks

 

They will be tucked under the truck, and probably rub the leaf springs under a hard turn. Stock back spacing is 4.5"

 

You may not need flares at all. I have 36x12.50 16.5s on my 79 f-350 and they barely stick out of the fenders, but idk what the backspacing is on those wheels. I have 33x10.5 16s on a 75 f-150 w 4in backspacing and they are still tucked under the fenders. You shouldnt need much flare if any, but i would suggest getting your wheels and tires put on and then measuring to see what u need.