If it were me, I would add some airbags (if you don't already have 'em).
Also, I would think you would definitely want to upgrade your wheel cylinders to the 3500 rear wheel cylinders if you haven't already done so.
In fact, seeing as how you're pushing the envelope a lil' with repect to your 2500's brakes, I would also suggest a complete brake overhaul with stainless kevlar brake lines front and rear, carbon kevlar pads and shoes, and a thorough flush with high end brake fluid at least once a year. I think it was Y-knot that posted something saying that rear drum can outperform rear disc if they're kept adjusted manually.
And then maybe a Brake Smart brake controller. If I did all that, then I would be comfortable pulling that 5er so equipped.
I am slowly upgrading my '94 2WD 2500 to pull my 15k Hitchhiker 5er, so I have a spare TV.