If it is stretched out it was improperly removed.Don't try to straighten it.They bend easily,and a tire iron will ruin one if you try to pry it off the wrong way.That usually happens when somebody tries to remove the ring when the tire bead is still up in the ring lip just a little.If the tire is down enough,the ring can be popped off with a screwdriver.When you put it back on,it should make a nice snap when it seats.Those rings are still available new,they are made by both Firestone and Borman.Truck tire stores used to have them,but tube type truck tires are almost a thing of the past.If you can find a good truck tire place,you can find a profile (end view)of the ring in the book.Clean the seat,or groove in the wheel thoroughly.Not wire brush it,a brush will leave the hard lumps behind.Get right in there with a file if you need to,no burrs to hold that rim out.Guys get hurt because they did something wrong.I was shown the right way by a man with a dent in his skull from a rim.I did hundreds before the contractor I worked for went to tubeless in the early 80's.