Rebuild Questions

I'm in the middle of an engine rebuild.

I will be installing new pistons, rings, piston pins, gaskets, and oil seals....

So what else might be good to replace while everything is apart? Clutch disks? Any O-rings? ??

Cylinder head is completely apart, looks good. Valve seats are clean. Is lapping necessary? How about valve seals?

I know, lots of questions, but I'm not in any hurry and any help/suggestions would be appreciated.