[bazar01]

I will answer my own question.

The studs are spot welded on two spots of the flat head.
With a dremel cut off disc, I only have to put a small cut on both spot welds and wacked the stud with a hammer.
The broken stud remains came off the back side of the flange.
I was surprised to see the studs were loose fit on the flange holes.

Easy enough.
Now I have to find some SS bolts and nuts.