Oxygen Sensor

[Zedman]

I have an '81 Avanti II with the dreaded Computer Controlled Carb/ignition/TC lockup controls.  I expect the Oxygen sensor is probably stonkered given its age and thought I'd better research a replacement. This is proving more daunting than I thought. To cut to the chase... Does anybody have any knowledge of a direct replacement for the two-wire O2 Sensor on these cars?  

[AG-R3]

Google is your friend ( most of the time)

A 1981 305 SBC (Small Block Chevy) engine that was part of an original equipment system uses a 2-wire, non-heated oxygen (O2) sensor. The 1981 model year generally utilized an early, single-wire or two-wire narrow-band O2 sensor design. 
Recommended Parts
You can find suitable replacement parts using these references:
AC Delco (OE Style): Original Parts Group lists an OE style 2-wire sensor, part number L980047, which is a direct fit for 1980-81 GM vehicles with a 305 engine.
Bosch (Universal/OE Type): Bosch offers both universal and specific fit options. The OE replacement parts typically have a 2-wire lead configuration for this model year.

Bosch Oxygen Sensor: 2 Wire, 12.48" Long, Non-heated, Exact Fit
Part # 12028