Deezdrama, Here is the question you posted on the other forum, "Whats the biggest size tires I can run with on my STOCK suspension e350 SD with fender/bumper trimming? Anyone done this?" Myself and others answered your question accurately. Most said 265/75R16's because that is about the biggest you can go without doing more than "fender/bumper trimming", assuming you still want to be abled to turn stop to stop and go over speedbumps. That is why WeldTec accurately told you the same answer above. 285/75/16's rub on a regular Quigley 4x4. Trimming front fenders from about 1/2" in front of bottom fender bolt up to a point a few inches lower than the first inner fender bolt will gain you a small amount of clearance at rear of front tire. The bumper needs to be trimmed or spaced forward. You will have to use rear wheel spacers for the rears or offset wheels for 265 and up or your rear inner sidewells will rub with any load on or over bumps. Trimming is fine but you could gain more clearance in far less time with new 1 and 1/2" coils, extended radius arms, a 1" body lift, etc. If you want the best drivability and more suspension travel with 285's, you will have to go further with bent I-beam kit like WeldTec, and others offer. I personally think Ford vans look best on 35's, but the answer to your question is NOBODY is successfully running anything larger than a 265 on a completely stock van.
View attachment 362077 Here is a pic of another place even 265's will rub on your van. Small lower oval, outlined with blue marker for clarity, is actual rub mark on drivers side floor. It is right below brake pedal. Larger outlined oval is amount that needs to be cut and re-welded for sharp left turn clearance.
Trim away all you want, but you might reconsider complaining when intelligent van builders take time out of their day to answer your questions. Cheers!