I have removed them to do crank seals with an impact gun. You need a 12 point socket and a 1/2" impact gun.extracting them if you can is going to be best, It takes a big tool bolted to the crank pulley to keep the crank from turning when you break the crank bolt loose.
The tool uses the 4 harmaonic balancer holes to secure itself to the crank pulley. The crank bolt is torqued to alot( I can't remember what it is but it's a bunch.
Nice work. That takes patience, but obviously you have that.