One common method of "stretching" the capability of your truck is ignoring the GVWR and instead going by individual axle ratings. On a 1500 truck this is usually good for an additional ~400lbs of payload on the rear axle.
You will likely need some suspension help to support even the rated payload and keep the truck from sagging excessively.
Just going over GVWR does not mean that you are instantly "unsafe." You've voided your truck's warranty (if they catch you, unlikely), and you may not like how the truck handles the load (definite possibility), but you are not necessarily unsafe. Poor maintenance, worn tires, and bad driving habits contribute to you being unsafe far more than a couple hundred extra pounds.
Frankly the biggest issue you need to worry about is if you will like driving the rig. Different people have different tolerances for different driving conditions.