Which HV Battery to Keep

2006 with 299k miles with a Toyota battery replaced about 100k miles ago. I bought the battery from a good Prius mechanic out of a 2007 customer was parting out and they installed it into my 2006. Toyota battery had been replaced about a year earlier. I've driven it about 85k miles. Been getting catalytic converter P0420 codes for a few years (I just clear codes and drive). California smog check due and it won't pass. Got red triangle for overheating engine. Shop testing indicates head gasket failure. It does burn oil and I may have not kept engine filled adequately and upon examination by shop found the serpentine belt worn enough to not always engage water pump depriving radiator adding to the overheating condition. Belt and pump replaced. Faced with more repairs than I wanted to deal with and too $ to pay for, I bought a 2007 with 160k miles on it. My commute is about 140 miles per day at high freeway speeds. Repair records show a couple of minor oppsies, but nothing major.
I am working with someone who may buy the 2006 and will tackle the head gasket and catalytic converter on their own. The buyer knows it is likely I will swap HV batteries. I don't hide things from buyers.

I think I know the answer, but should I swap the HV batteries to put the ~100k mile HV battery from the 2006 into the 2007?

 

Correct, the battery in the '06 was purchased from Toyota in 2015 by someone else who parted it out in 2016.
I will be meeting the person interested in the '06, with all of it's challenges, this afternoon. The buyer is quite willing to do the engine and catalytic converter work on the vehicle.
I've been driving the '07 all week with the 160k battery, and based on what I know of the original owner I bought it from, the condition of the vehicle itself, and how it has been behaving this week, I think this battery was used modestly and will last quite a while. The original battery in my '06 (which I bought new) was pushed hard throughout it's life with me and it started throwing codes at 186k miles, and I finally replaced it at 205k miles in 2015.
BTW, for those who see the time gap between failure and installation of the Toyota battery, I installed a Dorman battery which failed twice within about 8000 miles, so I returned it and installed the used Toyota battery (all done by a reputable shop).