As others stated, location will play a part in value. Honestly, Rio's are not all that rare overall. Some colors are more rare like the Aqua Pearl, Impact Orange and Emerald Green. The Moss green color is the most common color on the Rio. Looking on MP in my area of central Florida, there are currently 12 Rio Grandes for sale within 500 miles of me. 5 are the Lt. Pearlstone and 4 are the Moss Green, 1 white, 1 rattle can and 1 Jurassic clone. Several of them are price reduced, even at 6k. In my area your range would be realistically around 5,000 probably with no top and the faded paint. You say it's basically stock minus the wheels so that is a plus for you and assuming no real rust or corrosion on the tub or frame. I'd probably ask 6k and see if you get any offers.