You've chosen a great factory WSM. IMO it's the best factory WSM available. Your M70 is a 1 in 10 twist, and it will shoot whatever bullet you want it to, even up to the Berger 230. Don't settle for recommended OAL, load out closer to the lands. You'll be able to fit up to around a 3.000 OAL in your magazine.
I've tried several different powders and my favorites are the slow powders with either a 210 VLD, or a 230 Berger OTM. My favorite powder is IMR 7828ssc. It's an extremely consistent powder at all temps with great velocity. Another option is 4831sc. It's a lot slower, but it's accurate.