October pheasants aren't particularly tough anywhere. Assuming a decent hatch, a strong majority of the roosters you'll be shooting will be birds of the year. They're not fully grown yet. You may well run into roosters that don't look like roosters, and you won't know they are unless they make a sort of juvenile squawk. If your buddy has decent dogs, you should get quite a few relatively close shots. The exception to that would be a day with very strong winds, which you do encounter in the Dakotas. Then they're going to be more jumpy and you may want to have some 3" shells along, just in case. Or a 12ga.
I've hunted pheasants in ND in mid-December, which is a very different game. I arrived at the end of the day, with a couple guys in my group just coming in with their birds. Those roosters were packing more fat than any wild pheasants I've ever seen. The only change I made was to switch from 1 1/8 oz 6's (I was shooting a 16ga) to the same load in 5's. Worked well when pattern intercepted bird. But one reason I prefer 6's rather than 5's most of the time: More shot (225/oz vs 170.) And if you don't happen to center the bird, 6's are plenty big to break legs and wings. And if you break a wing and a leg, you stand a very good chance of recovering the bird.
