I doubt it,but you never know.I dont even want to know why would want to do this.If they were available they would cost about 600 bucks for all 4,so just buy new 6 lug wheels,its cheaper,and safer than adapters.
Mario, let me guess, you're thinking about swapping axles? You have a 1/2 ton now and want to put a 3/4 or 1 ton rear under it and run the same wheels/tires all the way around? If so, ask about that because there are a lot of neat options for keeping your six lug wheels, or going to all 8 for that matter.
Tried adapters a long time ago. It was for Ford wheels on a Pontiac and the results were.... The tire loosened up and departed with no warning going into an oncoming car dead center.
I had a bad lesson and learned this...I would never run any kind of wheel adapter EVER again I was lucky that no one was hurt or killed. It is just simply not worth the risk.