Updating piston rings, what else to do while there?

How many miles on the engine?

IMO, it will be a lot easier to just replace your existing engine with a used JDM engine.

Read this recent post, https://priuschat.com/index.php?posts/3600960

 

The revised rings require the revised pistons, part nos in attached.

this 3-part video is quite thorough:

 

I would send the head to an automotive machine shop for inspection and repair if needed. Some warn of taking too much surface off if warped due to potential timing issues.

The number one problem we hear about is the timing chain off by a tooth requiring rework. Follow Toyota's instructions to the letter including the short reverse rotation to release the tensioner.

Leaks at the timing chain cover happen but if you do yours engine out it should be easier to do right. Unless you have the engine in the car again and then find the timing is off.

Others fail to reconnect all hoses or connectors.

Still others spill coolant into the ac connectors causing problems since high voltage to the compressor is shutoff when any ground conduction occurs. Sort of like a built in gfci.

Allow plenty of time. You are bound to need more tools and parts.

 

Some people have continuing problems even after attempting to clean it up. Best to carefully protect both the high voltage and control connections, cable ends and especially compressor end. Occasionally the compressor has to be replaced. Its unclear what the failure mechanism is but the compressor has an ecu.

 

I'd second having the head sent out to a reputable machine shop. One of the rare occasions I wouldn't use an old-timer with lots of experience. IMHO; Aluminum heads are a different animal that requires a different skill set and modern equipment to be done properly. They will replace valves and guides, if necessary, and valve seals to prevent top end oil leaks.
Make sure you put everything back in the same place, don't mix up piston bearing and clamps. I'd mark them before taking them apart. Some pistons are directional; I haven't taken one of those apart; so pay attention to the marking stamped on the rods and sometimes inside under the piston.
I would replace at least the timing chain, tensioner and any plastic guides; there's going to be some stretch to that original chain. Might as well take care of that while your there. Replace the water pump too, while it's out. I understand that they get intermittent as they age. You don't have a temp. gauge, just a dummy lamp.

That's all I can think of for now... Good Luck...

 

The "built-in GFCI" function is monitored by the power management control ECU, for the car's whole high-voltage system, and reported by the code P0AA6. Inside the compressor is a DC to three-phase AC inverter/motor-controller, and the P0AA6 will have a subcode 614 if the ground conduction is on the DC side of that, or 611 if on the AC side. The P0AA6 code has car-wide consequences: the car won't go READY, if the code is present when starting. If the code is detected while driving, the triangle will light up and you can still finish your drive, but not go READY next time.

That's the kind of consequence that can be temporary if you are able to correct the conduction to ground; clear the code then and you're good to go.

But it's also possible for coolant getting inside the compressor to have the other usual effects of getting water into electronics, just letting the magic smoke out for good. You might see that in B147x or B1498 codes from the HVAC system, and the air conditioning not working while the rest of the car still does.