According to the information I found on my truck (2002 F-350 SD CrewCab DRW, 7.3L Diesel, Auto Trans)
truck total wt = 6,577#
Payload = 4,620#
GVWR = !!,200#
The GCWR = 20,000#
(Gross Combination Weight Rating including truck weight, passengers, cargo and the loaded trailer)
But the Max...