Why do you say not to weld them?
Ive been welding 20 years 40-60 hrs a week stick,mig, and tig and trust my welds not to crack over a chinese kid who learned to weld last week.
I mentioned paint because im not sure what grade of stainless these are or if they will rust. The look of rust isnt an issue to me its holes/cracks in the headers a few years down.