What else to replace with 2013 Prius Two head gasket?

I don’t have time to do it for you, but once you’ve settled on the main scope of work, I’d suggest to read carefully through the Repair Manual (more info) procedures, including all the cross-references, and make a list of all the non-reusable parts, mentioned as “new” in the Reassembly or Installation procedure text or shown with the ⚫︎ symbol in the Components illustrations, that will also need to be replaced as part of the job.

This review will also help you identify fasteners, trim clips, special service tools, and other items you may need. (For example, do you have a 10 mm bi-hexagon wrench?)

 

For the head bolts.

there’s some head gasket related Repair Manual excerpts, first HG related link in my signature. And second link is to @The Critic ’s thread.

 

Yes for some reason it was already in my toolbox and I hadn't worked on ZZ engines at that point. Except for AC comp replacements and alternator etc. So I'm not sure how I had the thing but it was in with my bits like torques and Phillips and security torques and all that mess I was actually quite surprised that I had it. And then I didn't use it except to disassemble the engine that broke just to remove parts.