My understanding is that when Winchester re-tooled with computer controlled machinery a few years back, they switched back to the pre-1964 design / features... If so, would a new or late-model model 70 be a good choice?
Absolutely! The design is why it performs so well. It is also important to pick a cartridge that has a taper to it’s body. (From the base to the shoulder) This is why the taper was designed into most cartridge types. It greatly aided feeding and repeat shooting. It was vital in bolt action rifles used in combat.
Any good reloading manual will outline the best rounds with these characteristics. But for Brown Bear, I would want at least a .338 Win. Mag. (Which has a moderate taper)