Offhand, I can't remember the spec on the stud for the 6.4 head studs, but I can assure you guys I've never broken a socket doing up 6.4 studs, and broke 'em doing 6.4 stock bolts! LOL.
The 6.0 studs torque to 210FT-Lbs now, and I'd say the tensile force put on the stud at 210 is comparable or even less than the factory bolts with the torque to yield spec.
Never had an issue using studs, only thing I advise anyone to do is make sure the blind holes are cleaned out before trying to install the studs.