I heard a couple of years ago that Tim North at Broughton barrels had a button for 8 twist .264 that was turning out some very nice barrels. So we ordered one for my father's build in .264, and it shoots better than he can. So I would echo BobT and suggest that you pursue that option.
Another key question is how tight a neck are you going to use. I have a .290 neck on mine, and my father's is more like .294. I wouldn't go any tighter than that.
