When you look at the specs of the individual components of the Ram 1500s you will see that there is a lot of cushion built into the payload. I believe most of it is to keep that awesome soft ride. Overloading by 500 lbs won't overload any individual components that I'm aware of.
I would consider stiffening it up though. Possibly better tires. There's many suspension upgrades available for the non-air ride Rams. The air-ride likely won't need upgrades.
I agree that you should get more truck, but you could make the 1500 work. A basic Laramie has plenty of bells and whistles while still typically having a couple hundred pounds of more payload than the Limited. JMHO