For thermocouple interfacing I’m currently considering the analog devices AD849x (4,5,6,7) series of thermocouple interfaces. Analog devices has an application note (AN-369) that is for another interface but covers how to read multiplexed thermocouples. Instead of the multiplexer listed in the application note I am considering the ADG707. This ic will run from a single supply of 5 volts but only has a rated analog signal range to VDD (5 volts). This limits the range of temperatures but since I will also run the AD849x on 5 volts this should not be a problem. The maximum temperature is theoretically 1000 degrees C since the output of the thermocouple interface is 5mV/°C.