IF, as you stated now that your truck is a 1500HD...JIMNLIN is right...it's a far more "beefier 1/2 ton then GM's 'normal" half ton pick up during that time frame....OP needs to look at his RAWR and weigh his truck to see how much pin weight he can put in the bed of the truck.
I think he needs to weigh his truck and whatever amount is on his drive axle, add an additional 200# for a 5er hitch, and go from there....Use GVW of 5er and take 20% of that to get a ball park idea of what pin weight you might be adding to the weight on the rear axle..
BUT OP also mentioned SLIDE(S)...how heavy of a 5er is he planning on getting. Everyone knows that one slide is going to add more weight and more slides are going to make it even heavier....Do the math and use some common sense and try to err to the side of safety in picking out a 5er you're going to tow,