This comes from an older thread on the FTE site. i don't have any documents to confirm but the members are legit.
This information is taken from the Ford sales manual:
F1 = 1/2 ton
F2 = 3/4 ton
F3 = 3/4 ton Heavy Duty
F4 = 1 ton
F5 = 1 1/2 ton
F6 = 2 ton
F7 = 2 1/2 ton
F8 = 3 ton
This information is taken from the Ford sales manual:
F1 - max payload of 1480 lbs, 1850 lbs including body & equip.
F2 - max payload of 2428 lbs including body & equip.
F3 - max payload of 3340 lbs including body & equip.
F4 - max payload of almost 5000 lbs, 5980 lbs including body & equip.
F5 - max payload over 8000 lbs, 9570 lbs including body & equip.
F6 - max payload over 5 tons, 11,305 lbs including body & equip.
F7 - max payload of 12,865 lbs including body & equip.
F8 - max payload of 15,465 lbs including body & equip