I went with a 3 groove 1-12 twist on my 358 win rebore. I would recomend the same. Accuracy has been great and the 1-12 will allow you do use any 35 cal bullet on the market.
My 35 Whelen is a 3 groove 1-14 twist barrel and it is better than a .5 MOA but I am not :shock:!
It sure likes 225gr. ABs over top of RL-15.
Looking forward to your range report with photos I hope.