I use a hand held type from NAPA for tuning. Its a older model with a tail pipe sniffer. Its real handy when setting multiple carburetor idle screws. As far as a everyday gauge, I'am not sure you would get much out one, it might scare you to see how rich and lean they run at times! I set my mono-jets to idle and run in the fuel injection range, I figure if its good for my '03 Toyota, then its good enough for a '70 Chevrolet.
You can just install a 02 sensor and read it with a multi-meter, if you do a google search, there are a few sites that explain how to read the sensor. 02 sensors create there own signal so no power is needed for them, the multi-meter simply read what the sender is doing and you convert the readings to ratio's. I believe any 02 sensor will work and you want it in the hotest part of the exhaust stream, usally about 6 to 8" from the header outlet or exhaust manufold outlet
Joe
