I have a 2006 with no issues currently, is there a compelling reason to go gen 2 over gen 1 for a preventative install? We have no emissions or inspections here to worry about.
I run techstream on an older apple laptop, virtualbox and run a VM. Supposedly there are some good and cheap scanners these days, I've seen this mentioned a few places:
https://www.amazon.com/Scanner-TOPDON-ArtiDiag500-Transmission-Diagnostic/dp/B08XK3DJ42
Wil Oberdick at Dark Illusions Fabrication (Best found on Facebook) makes a harness that uses the rotary Toyota factory switch which fits into the black square dead plate to the right of your steering column. That’s about as factory looking as you can get.
If there is visible heavy rust it's likely the frame has very little strength left somewhere, so who knows how long you might get.
And yes, lots of people have posted their trucks over the years or ones they went to look at that had either catastrophically failed or were right on the verge.
You could have a a failing water pump given all those symptoms. How much coolant have you put in it? Could even be a head gasket leak. There are a few other places known to leak that could be dripping down there.
Almost every GX with air suspension will have a tiny leak somewhere that the compressor has to run occasionally to top up the system. Leaving it off doesn’t allow this to happen.
Turning it off is only really for maintenance.
Yeah... rust belt vehicle I dunno. Maybe some areas got better attention for undercoat over the years? I would be concerned some of that rust is inside out instead of surface.