Where to weld in O2 bung for SC'd car?

Ok members help me out...
Car--1999 NB JR supercharged
Location-- Northern California
Issue-P0421 code(precat)
So I obviously have a common issue, but I want to take advantage if I can. I bought the 01+ exhaust manifold to swap. I'm not worried about the visual cause my supercharger in combo with the stock heat shield should cover it just fine. But I will have to weld a new bung for the front o2 sensor.
So where do I relocate the front o2 sensor to that was in the precat?

In the down pipe.

http://mazdaroadster.net/showthread....tall-Not-Today!!!!

For passing visual, either use a manifold blanket or wrap it. The years I spent in CA, I ran a JR header and a heat blanket. Although the header was CARB legal, the blanket covered it and an inspection tech never lifted it to check.

It would be a good thing to have anyway, the SC will get hot enough without the exposed manifold directly under it.