Thanks MrCIG. I'll have to replace the stock hitch with a Titan, if for no other reason than it is a bad azz looking hitch

The stock hitch definitely has to go. My 419 is not the same weight as your 400 but it is was still over the factory hitch rating.
I installed a CURT mfg 2 1/2" receiver hitch and got a forged draw bar and ball for an 18,000 lb rating. As a "15" model truck you may have the 2 1/2 receiver then you just need the rest of the parts for higher tow rating. My "06" Duramax only had the 2" receiver rated at 12.000 which was a joke for a DRW 3500.