Thanks for the help & information on the barrel replacement. Finally got the upper lapped and barrel installed. Used the vice block, no issues.
The new barrel was needed so the threads of the brake would extend out from under the handguard enough for my new Form 1 accessory. Perfect fit & testing went better than I imagined.
"A pistol is what you use to fight your way back to the rifle you never should have left behind!" Clint Smith, Thunder Ranch