I think the .35 Rem has an odd head size.
This is often repeated, but insignificant. Remington used the same bolt for 308/30-06 and 35 Remington. The minor difference in head size just doesn't matter.
The twist rate in the 35 Rem barrels is fine. Mine shoots great with 250gr jacketed bullets, and have tried 270gr cast with good results as well.
With that said, a Remington 760 in 35 Rem usually commands a premium price, so if you don't already have one, it might be cheaper to rebore & rechamber a 308 or 300 Savage barrel.