I'm replacing the old school threaded steel fork and headset on a '70s Raleigh with a NOS steel Tange threaded fork and a Shimano 105 headset with sealed cartridge bearings. I chose the Shimano 105 primarily because it had the right stack height. I wandered down to the LBS to have the fork milled and the crown race mounted. They told me that since I was using a headset with cartridge bearings rather than loose bearings, that it was unnecessay to have the fork milled and crown faced. I just needed to have the crown race pressed on and I am ready to go. Being a skeptic by nature I thought I would get a second opinion from the doctors here. Are they correct?
Any bearing needs to be mounted squarely, sealed or not. In theory they are not correct in their reasoning, but practically, I have found the Shimano cartridge headsets to be forgiving of misalignment. If the headset runs smoothly without sideplay, go ride.