I'm not sure of any areas in Montana that produce trophy bucks year after year. If you are looking for a decent buck with 12" horns or so I would not hunt opening day and do your hunting more in the middle or at the end of the season. Opening day of antelope season can be crazy, hunters feel they are missing out with other hunters on the prairie and usually shoot a smaller buck, thinking if I don't someone else will! If you wait till after opening weekend, you may have the whole praire to yourself, time to soak in the rolling hills, the coyotes, eagles, etc. Get a good spoting scope, look over ever goat in the area, before you shoot one. Thats the best advice I can give.