As for removing the crank wick, I remove the wick and drive a piece of slightly tapered brass into the hole. The flywheel will not accept a ball bearing without machining and I doubt there is enough material to have a ball bearing pilot bearing. I have sometimes used a needle bearing for the pilot bearing, however the factory bronze bushing works just fine with a finger full of grease smeared in it before putting the tractor back together.

  The older solid 8-1/2" discs were designed to use alternating think and thin clutch disc segments to help smooth out engagement, with the theory that only half of the facing would contact upon initial engagement, nowadays just use the spring loaded center disc for smoother engagement.  I put solid discs in pullers and spring loaded centers in farm tractors.