[Drifter]

I'm reasonably confident the skirt wear was from overheating since the piston-to-wall tolerances were essentially identical but only a couple of pistons exhibited the wear.

Regardless, the machine shop called with bad news. The rear head is cracked below the valve seat which was what was pressuring the coolant. They can weld it, but it would add 3 weeks and a couple hundred extra dollars. At that point, I'd be looking at paying $1300-1500 in parts and machine shop fees to rebuild an engine towards the sloppy side of the tolerance limits since they can't do a proper bore on the 3MZ with their equipment (and the other machine shops are turning away work).

So I ordered a documented 126,000 mile engine from LKQ for $1250 shipped (and should be here in 5-7 business days). Their listing showed a rear-ended highlander with a 126,000 odometer picture. Plus the VIN matched a car which last sold with 95,000 miles in 2019. Assuming the Vin on the delivered engine matches the Vin on the car, I think it will likely be as good as a re-ring rebuild.

So basically I'm back to where I was a month ago, only now I'm committed to doing the install myself. On the plus side, what I would have paid in labor to a shop I've gained in tools and some extra parts (like a CV axle, new control arm bushings, new rear coil-on-plugs, etc).