Something else to consider is how far do you want to go?
Ideally remove the heads and lap all the valves in. This would mean an assembly clearance and then later a checking clearance. You may use new half rings which again means assembly and checking clearances. Even if you re use your half rings they may well settle differently in a new shim therefore requiring another adjustment.
Deciding on what you want to do is harder than the actual job. LOL
Enjoy