Original inline 6 flywheel, please help

[Critter]

I come from the 67-72 world so please forgive me if this is a dumb post. Google has let me down up to this point.

I am working on a 59 Apache that is basically all original. Inline 6 (I forget the displacement, pretty sure there was only one at the time) with 3 speed manual on the column. The clutch is trashed and the flywheel is pretty bad as well.

THIS FLYWHEEL HAS TIMING MARKS ON IT THAT YOU VIEW AROUND THE SIDE OF THE ENGINE BY THE STARTER. Otherwise it looks fairly similar to anything else you would see from the 60s/70s/80s.

The disk and pressure plate look very "normal", the disk is 10 inch. Is this flywheel available aftermarket? I can't seem to find one and with the grooves in this one I'm pretty sure it can't be turned enough. Is there a newer flywheel that I should use and just find a way to time the engine off the balancer like a later model? The disk and pressure plate show to be available at any parts store, looks like they were used for years. The flywheel is my concern. Any guidance is appreciated.