I have used Winchester .270 WSM brass, Norma .270 WSM brass and most recently expensive Nosler .270 WSM brass. The Nosler is the best, it is very close in weight. The extreme spread was like .022 grams for the cases I weighed on a Laboratory balance. Regardless of brass, anneal them every 5 or 6 full power shots and they will last many cycles. Winchester metalurgy seems excellent but the primer pockets will need work. I have sorted cases only twice and they shot a little bit better than unsorted cases.
You need as much neck as possible so I would not be a fan of a reamer based on the 7mm WSM
neck position. The brass will make 6.5 WSM cases.
The overall length of the Model 70 magazines and Mauser 98 Magazines will easily accomidate the long for caliber bullets that excell at long range. I would have a Tubbs speedlock kit installed for either of these actions but Tubbs makes them available.
Both Wilson size dies and Redding .270 WSM bushing dies make excellent 6.5 WSM dies. I use a full length Redding bushing die most of the time for my 1885 Highwall and the Wilson (neck only) for the Model 70 because it has more camming power.