Some people are under the misconception that as the AISI number increases, so does the alloy content, i.e., Cr and Ni increases as the AISI number increases. That is incorrect. There is no direct correlation between the AISI alloy number and the alloy content.
Compare the alloy contents of several common Austenitic stainless alloys; 304, 308, 309, 310, and 316.
AISI 304 308 309 310 316
Cr 19 20 23 25 17
Ni 9 11 13 21 12
In the case of the lower alloy numbers, the alloy content does increase, but the alloy content of 316 drops back to something between 304 and 308, but with the addition of Molybdenum. The percentages I've listed are about the mid-range values for Chrome and Nickel.
One way to determine which filler metal is appropriate is to use the WRC diagram to approximate the Ferrite Number and shoot for something between 3 and 10 and make sure you are in the Ferrite to Austenite transformation range for the solidification mechanism.
Best regards - Al