Catalytic Converter throwing off O2 sensor

Alright so I just bought an 05 4runner with the v8 in and the previous owner had the both catalytic converters taken off. It’s throwing the P0037 code and I’m wondering if there is a simulator that could trick the computer or if I need to replace the O2 sensor. Also, the guy said the transfer case was messed up and wouldn’t allow it to go into lo4, however I can hear the relay working and the actuator working but it won’t engage and causes the center diff lock light to stay on with an annoying beep. If y’all can help in anyway that would be great!