Ordering headers soon for my son's 85' TPI 305. Question? How/where do you hook up the O2 sensor? I see it is bolted into stock manifold. Is there a a threaded port/hole in the headers when they come? Planning on removing EGR and delete it as well as smog tubes/pump.

 

You'll probably have to weld on an o2 bung. It's best to mock up your exhaust then decide where you can best locate the sensor where it's not in the way of anything else. Which is probably why you'd be hard pressed to find headers with a bung in place already...that and some guys are running carbs that don't require o2. Best place to put it is on/near the collector where the 4 tubes come together. Keep in mind that you'll probably have to run a heated/powered o2 sensor once you go to headers.