My Actual weights and was scaled more then one time. My 97 4X2 extended 7.3 with 4:10 gearing
Unloaded Truck with hitch, 2 passengers and full of fuel scaled at 6040 lbs. Leaving 2800lbs for payload, actually the rear showed more then 3200lbs before going over tire loading. I have scaled my setup and am within all specifications listed in the owners manual and per weight sticker. GCWR with 4:10 was 20,000lbs
If you stay with a trailer under 12,500lbs GVWR your should be right at the limits of what it can do unless it has higher then normal pin weight. if a 97 or older truck, The 99 thru 2002 truck actually had lower payload because the Super Duty trucks got heavier and Ford did not change the Weight stickers on them till 02 or 03's. I could be off on the years but the 99 trucks had low payload. The 97 and older trucks have very good payload.