120 should be fine. You won't get higher from the bison - they drop double digit quality leather. I feel like I got a 102 or 104 once, but otherwise it's all been double digits. And going much higher isn't hugely helpful anyway, since presumably you're planning to infuse that, and the diminishing returns get really punishing after 130 quality. Bison leather's resistance scaling tapers off noticeably after 115, too. Basically, don't sweat it. You probably can't beat that 120, you almost certainly won't, and you definitely don't need to.