I have a 2007&1/2 2500 CC, it can tow 12300lbs. can I swap the rear end with a 2017 and get the tow cap that that year has (17,200lbs)

 

Tow rating involves more than just the axles..... Also, if you tow more than your truck is currently rated for, regardless of what modifications you have done, if there is a problem, your insurance company won't cover it, and the cops will write you a VERY expensive ticket.



Welcome to DF!

 

So, the answer is: No.

 

Short answer (as stated) no.

Long answer:
1. Your truck has leaf springs, the '17 has coils and airbags. Unless you intended to have the heinous amount of custom fab work required to make everything fit and function properly done, it will NOT bolt into your vehicle.
2. As stated above, much more goes into the tow rating. You can't just swap pieces and magically have a better tow rating. You want the better tow rating? Get the truck you need.
3. Also as stated above, regardless of modifications that would physically increase your possible tow rating (i.e. I put 4.56 gears in place of 3.92's on my truck, that doesnt' magically add to the rating. It simply makes it easier for me to tow but I couldn't legally exceed the rating for my truck), you cannot legally tow more than the vehicle is officially rated for. If you have an accident, someone gets hurt, etc you're on the hook for any costs, possible tickets and possibly a lawsuit.