I second what thegipper said. An OEM radiator is cheap compared to replacing a transmission. I'm assuming that your possessed HVAC is your HVAC control unit not working properly? If that's the case there is a guy on the forum here that repairs them. I had him repair mine and it was a really quick turn around.
Auto Climate Control Repair Services
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2000 SR5 V6 Manual 4WD
https://www.toyota-4runner.org/3rd-g...biography.html
2000 Limited V6 Auto E-Locker Sold 3/2022