It will tow MUCH more weight than the brakes will stop safely. What engine are you running? My 72 C-10 with a 350 4-barrel and a turbo 350 trans would handle 7,000 lbs. easily, but I had to have good trailer brakes and plan ahead for stopping with a max load. If you've got the 3/4 ton suspension and rear axle, pulling power won't be a factor, but those drum brakes will get you into dangerous territory in a hurry!
Jerry