Try finding one for a 75. I have another box for mine and it's dented and has rust but it's better than what I have. I can't guarantee I can find a good one. If I find one I'll post some pictures for you.
I talked to my guy this afternoon. He says he has a box in decent shape at his house. Now he says decent so I'm not too sure. He says the tailgate is junk but the box is ok. The only problem is being winter it is covered with snow. If you are still looking in the spring let me know and I will check it out.