Rich,
Do you have a 4000 series truck? They had 7,500, 9,500, 11,000, or 13,000 GVW (4100 and 4400 series). School Bus chassis also had different weight ratings.
I've corrected the information above.
Thanks,
Tim
Tim,
According to that chart you put up, mine must be a 4400, although I have not found that printed anywhere. It has QK in the number, and the wheelbase is 161".