I would get a 1:8 twist. My .260 sports a 1:9 twist and does manage to do very well with Lapua 139 gr. Scenars. The bullets have done very well out to 1050 yards.
The 1:8 gives you a wider selection of projectiles like the 140 Berger VLD and Hornady Amax, which can be finicky on twist rates. I have found the Sierras to stabilize fine with my slower twist rate.
Best of luck.