Check the front left corner of the 5er for the GVWR. This is the max weight the 5er is designed for.
Don't even look at what they list for the pin weight as this is the shipping weight.
Use the Gross (GVWR) weight and figure 20-25%. Divide by 5 for 20% and by 4 for 25%. This is the weight you could be adding to your truck.
Stand back and look at a 5er. Almost everything you put in it is going in the basement. It all adds to the pin weight.
I believe you'll not find anything over 6-7,000 lb gross that will match the number up for you. Check the sidewalls on your tires and see what they can carry. On 1/2 tons the tire weight rating are all over the chart.
Good luck findind a working combo that fills your needs.