Alloy C Mn P S Si Cr Ni Mo Others
301 0.15 2.00 0.045 0.030 1.00 17.00 7.00 - -
302 0.15 2.00 0.045 0.030 1.00 18.00 9.00 - -
304 0.08 2.00 0.045 0.030 1.00 19.00 9.25 - -
As you will notice in the above the nominal chemical composition of these stainless steels are very simillar with a slight difference in Carbon. The differences in the Ni & Cr are really no existence, the difference are within normal tolerenace range of these elements.
These are typical 18-8 SS I would not expect any problems different then welding each individualy.
>The weld must be leak free and withstand many cycles 300,000 to be exact.
Determine what the Max and Min stress levels and use a goodman or S-N diagram to determine failure limits.