that's a tricky weld actually, I have done a couple on motorcycles. If it were me, I would braze it.
You will need to clean the shiat out of it though, and I mean clean. Like shiny, bass boat clean, before brazing or welding. expect about two hours. That's why no one wants to touch it. PLUS, and this is a big PLUS, you will need to "de-coke" the inside, meaning get all the carbon off. Another reason to take it off. That stuff will just clog your cats if you leave the pipe in it's normal position.
a near-death experience is just god following "catch and release" regulations...
john (johnny) henley