Richie- I don't know what kind of oxygen sensor you found for a hundred bucks, but if it's not a wide band it's not worth buying. I got my setup from Innovate Motorsports....www.innovatemotorsports.com
It can be done the old fashioned way by constantly checking the plugs after each change. My expereince with these Rochester 1BBLs has been that they can be decreased in size to approximately 2/3 to 3/4 of original. Take it gradually though, because if you go too far you can put holes in your pistons.
Devin
