o2 sensor?

NOPE!

no

noooo

well, i want to build a device to monitor my fuel/air ratio, which requires an o2 sensor on the exhaust manifold somewhere, how should i go about installing it?

install it in the exhasust right after the manifold. you will need to weld an o2 bung on the pipe and I would suggest running a heated o2 sensor for a more accurate reading at all temps. especially when the engine is still cold