The earlier thick SW barrels work fine. Their just a little heavier and the lugs may had to be fitted for the factory flash hider. I wouldn't worry about it.
Were the lugs on early SW barrels not correct or withing tolerances? I have a 2000 SW5FS that I'm wanting to SBR. I just bought a HK 3 lug flash hider, I hope it fits when I get my Form 1 back and remove the fake suppressor.