As promised here is a video with the exhaust.
Here is a better picture of the O2 sensor. Can't tell from the picture but there is about a 1 - 2 mm clearance around it.
And another shot of the new versus old manifolds. Take a close look because the black is not all open port, just the smaller ring is open. The stock header also has a much sharper bend from the head than the Viking exhaust which has a much gentler radius.