[TurboVenom]

Place your sensor bung as close to the collector as you can. You should face it inward so as to keep it out of sight, don't place it under the pipe. It should be parallel to the ground, or upward from that position if possible. Putting it on one port won't work as it will give you incorrect readings.

Sensors must be 900 deg F to be properly active. Less than that temperature will skew the voltage readings and make your car run excessively rich. Cooler temperatures lower the mv readings.
I would recommend a heated sensor - four wire - for that application as the free-flowing sidepipes reduce the exhaust temperatures. And, depending on what fuel control system you plan to use, you will need either one or two...put ports on each side just in case.

My personal recommendation is the use of a wideband sensor and a fuel control system such as the XFI or FAST system.
John