I would recommmend the Innovative Wideband. Either the LC-1 or LM-1. These wideband O2 sensor come with a stand alone controller. I run a LC-1 in my megasquirted 122. Never a problem.

http://www.innovatemotorsports.com/products/lc1.php

http://www.innovatemotorsports.com/products/lm1.php

Paul

If you are not versed in the black voodoo arts of tuning carbs by ear, taste, smell and other mumbo-jumbo you will find an a/f meter beneficial in helping get the best power and economy out of your engine. The only 'hard' thing is that you'll have to have a bung welded in your exhaust system. I put an A/F meter in my 122 when I was putting in a new exhaust system, so it was just a matter of taking the pipe to a welder. More of a PITA if you're welding it into an installed exhaust, though certainly not impossible. I had mine mounted a bit downstream from where the y-pipe when from 2 to 1. The rest of the installation is simple wiring. They are more expensive, but I think you'll find a wide-band sensor/meter more useful. I think the brand I got was AEM, from Summit Racing.

You'll need a wideband O2 sensor a bung in your exhaust downpipe and a reader (JAW is about the cheapest around) then you can log the data to a laptop. There are many other more expensive solutions, but I have managed to put one together for around $250. I haven't had it in the car just yet as I've been occupied with other projects, but should get to it in the new year.