s40 second catalytic converter

[caspereeni]

My secondary cat on a "new used car" leaks around the edges and won't pass smog. I have a parts car with a pretty, shiny and new oem cat that I've removed. Problem is the old one has rusty nuts and I will have to grind them off. are these four studs I can press out or are they threaded? there is no head on the other side. anybody know what I'm in for? looks like grinding flush, drilling out and using plain old nuts and bolts. Of course that will be after a little heat, PB blaster and vice grips snaps of the 1/4" of stud thats still exposed. Thanks all!