Westin makes a line of bumpers that are very similar to the old "step bumpers" that were offered on many of the "Big 3" trucks of the 70's/80's/90's. They're rated at 8000/800...meaning 8K towing and 800 tongue. The loaded trailer weight you mentioned wouldn't give me much pause. And, depending on how you loaded the trailer, I'd venture a guess that you'll be in the 400 to 500 lb range on the tongue.
If you're concerned about the bumper letting go, you could rear-bias the load a bit (on the trailer), to mitigate some of the tongue weight. Just make sure that you retain some positive tongue weight. In other words, you do want the tongue weight to be enough that it squats the truck a bit. (*Negative tongue weight is a recipe for disaster on any vehicle.)
Here are the 1986 Gross Combined Weight Ratings (truck, trailer, passengers, load...the whole ball of cheese), for the 5.7L, with the corresponding cogs...
2.73 / 8500#
3.08 / 9500#
3.23 / 10000#
3.42 / 10500#
I suspect the ratings would be very close for your truck.