Here's a picture of the bottom of the car. The recommendations I have seen are that the sensor should be about 8" downstream of the collector for this sensor and system. As I understand it, the narrowband sensors need to be as close to the engine as possible, as they rely on the engine heat to heat the sensor element. The wideband for the Holley is self-heating, and it actually needs to be far enough downstream that it doesn't overheat from the engine's heat.
