We did nothing really different. Ford increased the GCWR back in 2010??? GCWR minus GVWR equals 7500lbs. We use a full frame extensions (same height and thickness steel that ford uses) all the way to the back. No departure angle (formed steel, smaller height in the back). This allowed us to use a 7500# hitch instead of a 5,000# hitch. Tested our 5,000 first, made some minor adjustments, retested, passed, sticker it for 7,500lbs.
We don't buy a different E450...we simply utilize the capacity they gave us. Of course it has to be tested, which we did and it passed.
PLEASE do not send questions via Private Message, my inbox fills up too quickly. Post questions in the forum as a new thread so that other users can benefit from the answers. Use Private Messages for sensitive information only (VIN, Contact info or things you do not want the public to see).