There are dual sensor kits that can power both and display both... for about 2x the price. Otherwise monitor one side, and make an assumption on how much the 2 sides may differ; I assume a difference of + or - 1/2 of an AFR point, based on reading a few examples of dual sensor readings on similar V8 engines. Even if you have dual sensors, you're still making an assumption that the 4 cylinders in each bank are not too far off from each other, but we all know that there are cylinder-to-cylinder mixture variations in any engine that vary with RPM and throttle loading, and yet we AFR tune to a whole set of 4. Plug reading is the back up to that IMHO.