If everything is stock , i would not cut a thing , something wrong , i never used aftermarket axles before so would not know , but i have changed these carriers alot in the last 30 years and had not problem with stock stuff.
i think there stock axles there no indication there not( ie brand names on them) but both are the same exact size and the passenger side just wont go in that last half in. like its hitting either the middle metal block thing the surgrip posi might not be lined up or the bearings might be hitting because of a spacer. but i dont think this is it because ive tried the other axle that fits on the other side onto the passenger side with the same results.