Dont know how or why you are going 5th wheel shopping when you did not weigh the truck...
Get the weights as I posted and you will know exactly what you can tow..
Its 10000 lbs for TT and 13500 for 5th wheel.. But thats with an automatic.. Thats per the tow rating list I found for your truck...
WE ASSUME YOU HAVE 3:73'S as all the 7.3 turbo diesals list this..
I think a manual trans will reduce this weight..
And as said pin weight and axles weights will be the issues..
Want to know what you can tow??
Go weigh the truck with full tank of gas and you in it... Get seperate axle weights at a cat scale..
Post back those #'s with the axle weights on the door tag of the truck.
And post the tire weight ratings at max inflation from the side wall...