While technically you're over the trucks GVWR that doesn't mean it's physically overloaded. Your not over axle weights so you should be fine. Particularly with upgraded tires. The GVWR on a class 2 truck such as yours is kept below 10,000 for legal reasons for the most part. No actual component of your truck is overloaded, except for rear springs, wheels, and tires they are all identical to a 3500 SRW from the factory.
Being over that much weight is kind of comical to TC owners. My own TC on my dually weights in at 13,100 on a truck with a 11,400 GVWR. I used to carry the camper on a 3500 SRW rated for 9,900 GVWR. The total weight on that rig was 11,150. Both trucks carried the camper for years thru thousands of trouble free miles in multiple states. I was not exceeding axle, tire, or wheel weights.