I wanted one for my 86 Sierra Classic real bad but they were not available anywhere (at least back when I was searching for them - maybe 10 years ago). I finally ended up fabricating one myself. It was a simple design but worked well. I had a Mile Marker 15,000 lb winch (POS BTW) that I kept in the bed and could shove into the rear or front receiver as needed.
It was basically just a receiver adapter that was welded to a plate in the back and with a gusset welded over the top. The rear plate was drilled to accept Grade 8 bolts that secured it to the front cross member.
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It was long enough that it stuck out past the bumper just a bit - but not so much that you'd bang your shin on it:
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Total cost was about $50.