New Header Bad News, Need Advice Please

[907mge]

In the old cast iron manifold the sensor is pretty well in the flow with it being between the two banks of 3 about 6in from the exhaust ports. Now what i'm trying to do is figure out if I can weld the downpipe to the header and still be able to get it out of the car.I'd like to wrap it further down and knock down some of the noise coming from it. It sounds like a v8 with open headers under the hood now. And I plan on moving the o2 location up the pipe much farther. It does make a nice inprovement in power though, not sure how much but noticable.