IMO - I’d pull the trans and outer tub; replace the doughnut and drain trap seal, clean up the trans and grease the cam bars, if you are reusing the drive make sure the pulley bearing has fresh oil. Even on machines that were whisper quiet the center post bearings have probably worn on the drive tube. A new set of bearings and seals are the assurance of not ruining an NOS drive tube. I’d also wash a few loads of heavy towels to test the agitator shaft drive spring inside the transmission. If it starts knocking or slips up in agitation the trans will need servicing or replace with one from an 80’s belt drive.
This also goes without saying - new belt and replace the pump while you have it torn down, and tend to rust issues with your favorite rust inhibitor paint.
Good luck!
Ben