I'm no expert but the numbers I think of are in terms of matching the GVWR of the trailer to the series of truck. As others have mentioned its more a matter of pin weight rather than tow capacity- all configurations of diesel engined 2500 or 3500 pickups will pull almost anything on wheels, ratings aside. I'm thinking 250/2500 up to 12K GVWR trailer, 350/3500 up to 16K and DRW for anything over that. I'm assuming you're talking Ram, if I were you I'd go all out and get a DRW with the Aisin trans and HO engine. Spend the extra $500 or so and get the factory fifth wheel package and drop your hitch right in without touching a wrench.
