Just picked up a BBK OR X-Pipe.

For my 1999 GT. I have bought a new flange for the passenger side and the guy gave me his old studs.

Couple Questions;
Measurements of the Studs in case I round off the head on the passenger side (again) ?

And do I need O2 extensions for the 2 rears? Or will they reach the back bungs?

And will I throw a CEL if they arent plugged in or if they are?

I will probably have an exhaust clip when I can get my buddies lift free; him and his retarded Chevelle Build