O2 sensor mounting

[Greg Woods]

I have an exhaust manifold that does not have a tapped hole
for an O2 sensor but their is what looks to be like a spot
that is tapped out when this manifold was used on FI type
engines.  

Does anyone know what is involved in tapping an
O2 sensor hole?  I think I read somewhere that you can't just drill
it and tap it with a normal tap because of sealing issues
between the sensor and the manifold once the assembly gets 
up to temp.  Has anyone done anything like this?

Any and all comments welcome!
TIA

Greg Woods
gwoods at symtx.com