Around here the easiest way is to lose the Title and have a new one issued as a home built trailer.
You may not be overweight though. Take it to a scale with your heaviest item on it and weigh it out. All that matters is what is on the axles for both the trailer and the truck, that you dont exceed your trucks GCVWR, and its GVWR.
Being only 600# over by your guesstimate, you may not be when you consider the weight on the truck via the hitch. A 10,000# load should have 10% of that on the ball so about 1,000# of tongue weight which will now be on the truck.
Chris