I will add a small resistor to shield MCU in case sensor goes short circuit, it is a harsh environment and it could happen. Ratiometric, exactly, thank you for that. And yes, will take multiple measurements and average it.
Next sensor is a stainless steel K type thermocouple for exhaust gas temperature measurement, capable of 0-1250C measurement.
For easy amplification of the thermocouple and interfacing it with SPI will use a MAX31855 board which takes 5V. Direct digital output temperature value, no amplifiers, no ADC 14-bit resolution, -200 to 1350C. Will try using Adafruit MAX31855.h as the library.
For this I plan not to use no other components.