You don't need the 3 wire sensors. The other wires are for
heating the sensor so that it gives the correct output under
a wider range of situations (cold start, long idle or down
hill with no load, etc). What you will need is a wide band
O2 sensor. The standard O2 sensor is accurate only around
14.something and outside of that won't make much sense. You,
on the other hand will want something that is accurate when
running rich since if you try to run your B20 at the same
range as a modern motor you will likely melt holes in your
pistons pretty quick.

There are lots of good sites that discuss O2 sensors.
chris