@andrewbriscoe
If I had to bet, 19mm socket and a pulley holder? I figure large sockets and specialty tools are rare outside of shops or the toolkits of tradesfolk and hobby wrenchers.
I bought an impact set from HF because I needed a 22mm. Got a cheap clone of the Oni Toyota/Lexus holder from Amazon. It's decent; cast, so no sketchy welds. But in hindsight I maybe should've checked if the usual suspects had a loaner for that. It's gonna be a $20 paperweight for the next decade or 90k miles.
@andrewbriscoe
They're expensive for a single socket but I've seen high mass sockets specifically for those nuts. I zipped mine off with an impact and a Pittsburgh socket, but it was from a deep set so maybe that extra mass helped.
For the holder I recommend a breaker bar long enough that it pins itself against the frame or ground while torquing. Might also make turning the nut easier for your inspection.
Good luck with it. It's a fun project I'm happy not to do again for a while 