I would suggest doing a bit more research. I suspect the GVWR of 10000# is more related to registration costs than to the actual load rating. States charge registration fees based on the GVWR and over 10000# can increase the charges.
Tires and wheels are typically what limits the safe load capacity and it seems there is no problem with them. The other issue is the rear coil springs. I would have avoided that and bought a truck with a standard spring pack that could be easily upgraded by a spring shop or with something like Timbrens.
