stainless welding wire

[Matt@RFR]

Here's a stainless filler metal selection chart, but to quickly answer your question: 304-304 joint would need 308 filler.

I found the above link with a search on "stainless filler selection chart" or some such...it's been a few years. I have it, a mild steel chart, an aluminum chart, and a magnesium and titanium chart on my office wall.